Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 4020 insertions, 0 deletions

diff --git a/dom/ipc/BrowserChild.cpp b/dom/ipc/BrowserChild.cpp
new file mode 100644
index 0000000000..9438f34689
--- /dev/null
+++ b/dom/ipc/BrowserChild.cpp
@@ -0,0 +1,4020 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "base/basictypes.h"
+
+#include "BrowserChild.h"
+
+#ifdef ACCESSIBILITY
+#  include "mozilla/a11y/DocAccessibleChild.h"
+#endif
+#include <algorithm>
+#include <utility>
+
+#include "BackgroundChild.h"
+#include "BrowserParent.h"
+#include "ClientLayerManager.h"
+#include "ContentChild.h"
+#include "DocumentInlines.h"
+#include "EventStateManager.h"
+#include "FrameLayerBuilder.h"
+#include "GeckoProfiler.h"
+#include "Layers.h"
+#include "MMPrinter.h"
+#include "PermissionMessageUtils.h"
+#include "PuppetWidget.h"
+#include "StructuredCloneData.h"
+#include "UnitTransforms.h"
+#include "Units.h"
+#include "VRManagerChild.h"
+#include "ipc/nsGUIEventIPC.h"
+#include "js/JSON.h"
+#include "mozilla/AsyncEventDispatcher.h"
+#include "mozilla/ClearOnShutdown.h"
+#include "mozilla/EventForwards.h"
+#include "mozilla/EventListenerManager.h"
+#include "mozilla/HoldDropJSObjects.h"
+#include "mozilla/IMEStateManager.h"
+#include "mozilla/LookAndFeel.h"
+#include "mozilla/MouseEvents.h"
+#include "mozilla/Preferences.h"
+#include "mozilla/PresShell.h"
+#include "mozilla/ProcessHangMonitor.h"
+#include "mozilla/ResultExtensions.h"
+#include "mozilla/ScopeExit.h"
+#include "mozilla/Services.h"
+#include "mozilla/StaticPrefs_dom.h"
+#include "mozilla/StaticPrefs_fission.h"
+#include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPtr.h"
+#include "mozilla/Telemetry.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/TouchEvents.h"
+#include "mozilla/ToString.h"
+#include "mozilla/Unused.h"
+#include "mozilla/dom/AutoPrintEventDispatcher.h"
+#include "mozilla/dom/BrowserBridgeChild.h"
+#include "mozilla/dom/DataTransfer.h"
+#include "mozilla/dom/DocGroup.h"
+#include "mozilla/dom/Element.h"
+#include "mozilla/dom/Event.h"
+#include "mozilla/dom/JSWindowActorChild.h"
+#include "mozilla/dom/LoadURIOptionsBinding.h"
+#include "mozilla/dom/MessageManagerBinding.h"
+#include "mozilla/dom/MouseEventBinding.h"
+#include "mozilla/dom/Nullable.h"
+#include "mozilla/dom/PBrowser.h"
+#include "mozilla/dom/PaymentRequestChild.h"
+#include "mozilla/dom/PointerEventHandler.h"
+#include "mozilla/dom/SessionStoreListener.h"
+#include "mozilla/dom/WindowGlobalChild.h"
+#include "mozilla/dom/WindowProxyHolder.h"
+#include "mozilla/gfx/CrossProcessPaint.h"
+#include "mozilla/gfx/Matrix.h"
+#include "mozilla/gfx/gfxVars.h"
+#include "mozilla/ipc/BackgroundUtils.h"
+#include "mozilla/ipc/PBackgroundChild.h"
+#include "mozilla/ipc/URIUtils.h"
+#include "mozilla/layers/APZCCallbackHelper.h"
+#include "mozilla/layers/APZCTreeManagerChild.h"
+#include "mozilla/layers/APZChild.h"
+#include "mozilla/layers/APZEventState.h"
+#include "mozilla/layers/CompositorBridgeChild.h"
+#include "mozilla/layers/ContentProcessController.h"
+#include "mozilla/layers/DoubleTapToZoom.h"
+#include "mozilla/layers/IAPZCTreeManager.h"
+#include "mozilla/layers/ImageBridgeChild.h"
+#include "mozilla/layers/InputAPZContext.h"
+#include "mozilla/layers/LayerTransactionChild.h"
+#include "mozilla/layers/ShadowLayers.h"
+#include "mozilla/layers/WebRenderLayerManager.h"
+#include "mozilla/plugins/PPluginWidgetChild.h"
+#include "nsBrowserStatusFilter.h"
+#include "nsColorPickerProxy.h"
+#include "nsCommandParams.h"
+#include "nsContentPermissionHelper.h"
+#include "nsContentUtils.h"
+#include "nsDeviceContext.h"
+#include "nsDocShell.h"
+#include "nsDocShellLoadState.h"
+#include "nsEmbedCID.h"
+#include "nsExceptionHandler.h"
+#include "nsFilePickerProxy.h"
+#include "nsFocusManager.h"
+#include "nsGlobalWindow.h"
+#include "nsIBaseWindow.h"
+#include "nsIBrowserDOMWindow.h"
+#include "nsIClassifiedChannel.h"
+#include "nsIDocShell.h"
+#include "nsIFrame.h"
+#include "nsILoadContext.h"
+#include "nsISHEntry.h"
+#include "nsISHistory.h"
+#include "nsIScriptError.h"
+#include "nsISecureBrowserUI.h"
+#include "nsIURI.h"
+#include "nsIURIMutator.h"
+#include "nsIWeakReferenceUtils.h"
+#include "nsIWebBrowser.h"
+#include "nsIWebProgress.h"
+#include "nsLayoutUtils.h"
+#include "nsNetUtil.h"
+#include "nsIOpenWindowInfo.h"
+#include "nsPIDOMWindow.h"
+#include "nsPIWindowRoot.h"
+#include "nsPointerHashKeys.h"
+#include "nsPrintfCString.h"
+#include "nsQueryActor.h"
+#include "nsQueryObject.h"
+#include "nsRefreshDriver.h"
+#include "nsSandboxFlags.h"
+#include "nsString.h"
+#include "nsTHashtable.h"
+#include "nsThreadManager.h"
+#include "nsThreadUtils.h"
+#include "nsViewManager.h"
+#include "nsViewportInfo.h"
+#include "nsWebBrowser.h"
+#include "nsWindowWatcher.h"
+#include "nsIXULRuntime.h"
+
+#ifdef XP_WIN
+#  include "mozilla/plugins/PluginWidgetChild.h"
+#endif
+
+#ifdef MOZ_WAYLAND
+#  include "nsAppRunner.h"
+#endif
+
+#ifdef NS_PRINTING
+#  include "nsIPrintSession.h"
+#  include "nsIPrintSettings.h"
+#  include "nsIPrintSettingsService.h"
+#  include "nsIWebBrowserPrint.h"
+#endif
+
+static mozilla::LazyLogModule sApzChildLog("apz.child");
+
+using namespace mozilla;
+using namespace mozilla::dom;
+using namespace mozilla::dom::ipc;
+using namespace mozilla::ipc;
+using namespace mozilla::layers;
+using namespace mozilla::layout;
+using namespace mozilla::docshell;
+using namespace mozilla::widget;
+using mozilla::layers::GeckoContentController;
+
+NS_IMPL_ISUPPORTS(ContentListener, nsIDOMEventListener)
+
+static const char BEFORE_FIRST_PAINT[] = "before-first-paint";
+
+typedef nsDataHashtable<nsUint64HashKey, BrowserChild*> BrowserChildMap;
+static BrowserChildMap* sBrowserChildren;
+StaticMutex sBrowserChildrenMutex;
+
+already_AddRefed<Document> BrowserChild::GetTopLevelDocument() const {
+  nsCOMPtr<Document> doc;
+  WebNavigation()->GetDocument(getter_AddRefs(doc));
+  return doc.forget();
+}
+
+PresShell* BrowserChild::GetTopLevelPresShell() const {
+  if (RefPtr<Document> doc = GetTopLevelDocument()) {
+    return doc->GetPresShell();
+  }
+  return nullptr;
+}
+
+bool BrowserChild::UpdateFrame(const RepaintRequest& aRequest) {
+  MOZ_ASSERT(aRequest.GetScrollId() != ScrollableLayerGuid::NULL_SCROLL_ID);
+
+  if (aRequest.IsRootContent()) {
+    if (PresShell* presShell = GetTopLevelPresShell()) {
+      // Guard against stale updates (updates meant for a pres shell which
+      // has since been torn down and destroyed).
+      if (aRequest.GetPresShellId() == presShell->GetPresShellId()) {
+        APZCCallbackHelper::UpdateRootFrame(aRequest);
+        return true;
+      }
+    }
+  } else {
+    // aRequest.mIsRoot is false, so we are trying to update a subframe.
+    // This requires special handling.
+    APZCCallbackHelper::UpdateSubFrame(aRequest);
+    return true;
+  }
+  return true;
+}
+
+NS_IMETHODIMP
+ContentListener::HandleEvent(Event* aEvent) {
+  RemoteDOMEvent remoteEvent;
+  remoteEvent.mEvent = aEvent;
+  NS_ENSURE_STATE(remoteEvent.mEvent);
+  mBrowserChild->SendEvent(remoteEvent);
+  return NS_OK;
+}
+
+class BrowserChild::DelayedDeleteRunnable final : public Runnable,
+                                                  public nsIRunnablePriority {
+  RefPtr<BrowserChild> mBrowserChild;
+
+  // In order to try that this runnable runs after everything that could
+  // possibly touch this tab, we send it through the event queue twice.
+  bool mReadyToDelete = false;
+
+ public:
+  explicit DelayedDeleteRunnable(BrowserChild* aBrowserChild)
+      : Runnable("BrowserChild::DelayedDeleteRunnable"),
+        mBrowserChild(aBrowserChild) {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(aBrowserChild);
+  }
+
+  NS_DECL_ISUPPORTS_INHERITED
+
+ private:
+  ~DelayedDeleteRunnable() {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(!mBrowserChild);
+  }
+
+  NS_IMETHOD GetPriority(uint32_t* aPriority) override {
+    *aPriority = nsIRunnablePriority::PRIORITY_NORMAL;
+    return NS_OK;
+  }
+
+  NS_IMETHOD
+  Run() override {
+    MOZ_ASSERT(NS_IsMainThread());
+    MOZ_ASSERT(mBrowserChild);
+
+    if (!mReadyToDelete) {
+      // This time run this runnable at input priority.
+      mReadyToDelete = true;
+      MOZ_ALWAYS_SUCCEEDS(NS_DispatchToCurrentThread(this));
+      return NS_OK;
+    }
+
+    // Check in case ActorDestroy was called after RecvDestroy message.
+    if (mBrowserChild->IPCOpen()) {
+      Unused << PBrowserChild::Send__delete__(mBrowserChild);
+    }
+
+    mBrowserChild = nullptr;
+    return NS_OK;
+  }
+};
+
+NS_IMPL_ISUPPORTS_INHERITED(BrowserChild::DelayedDeleteRunnable, Runnable,
+                            nsIRunnablePriority)
+
+namespace {
+std::map<TabId, RefPtr<BrowserChild>>& NestedBrowserChildMap() {
+  MOZ_ASSERT(NS_IsMainThread());
+  static std::map<TabId, RefPtr<BrowserChild>> sNestedBrowserChildMap;
+  return sNestedBrowserChildMap;
+}
+}  // namespace
+
+already_AddRefed<BrowserChild> BrowserChild::FindBrowserChild(
+    const TabId& aTabId) {
+  auto iter = NestedBrowserChildMap().find(aTabId);
+  if (iter == NestedBrowserChildMap().end()) {
+    return nullptr;
+  }
+  RefPtr<BrowserChild> browserChild = iter->second;
+  return browserChild.forget();
+}
+
+/*static*/
+already_AddRefed<BrowserChild> BrowserChild::Create(
+    ContentChild* aManager, const TabId& aTabId, const TabContext& aContext,
+    BrowsingContext* aBrowsingContext, uint32_t aChromeFlags,
+    bool aIsTopLevel) {
+  RefPtr<BrowserChild> iframe = new BrowserChild(
+      aManager, aTabId, aContext, aBrowsingContext, aChromeFlags, aIsTopLevel);
+  return iframe.forget();
+}
+
+BrowserChild::BrowserChild(ContentChild* aManager, const TabId& aTabId,
+                           const TabContext& aContext,
+                           BrowsingContext* aBrowsingContext,
+                           uint32_t aChromeFlags, bool aIsTopLevel)
+    : TabContext(aContext),
+      mBrowserChildMessageManager(nullptr),
+      mManager(aManager),
+      mBrowsingContext(aBrowsingContext),
+      mChromeFlags(aChromeFlags),
+      mMaxTouchPoints(0),
+      mLayersId{0},
+      mEffectsInfo{EffectsInfo::FullyHidden()},
+      mDidFakeShow(false),
+      mTriedBrowserInit(false),
+      mOrientation(hal::eScreenOrientation_PortraitPrimary),
+      mVsyncChild(nullptr),
+      mIgnoreKeyPressEvent(false),
+      mHasValidInnerSize(false),
+      mDestroyed(false),
+      mDynamicToolbarMaxHeight(0),
+      mUniqueId(aTabId),
+      mIsTopLevel(aIsTopLevel),
+      mHasSiblings(false),
+      mIsTransparent(false),
+      mIPCOpen(false),
+      mDidSetRealShowInfo(false),
+      mDidLoadURLInit(false),
+      mSkipKeyPress(false),
+      mLayersObserverEpoch{1},
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+      mNativeWindowHandle(0),
+#endif
+#if defined(ACCESSIBILITY)
+      mTopLevelDocAccessibleChild(nullptr),
+#endif
+      mShouldSendWebProgressEventsToParent(false),
+      mRenderLayers(true),
+      mPendingDocShellIsActive(false),
+      mPendingDocShellReceivedMessage(false),
+      mPendingRenderLayers(false),
+      mPendingRenderLayersReceivedMessage(false),
+      mPendingLayersObserverEpoch{0},
+      mPendingDocShellBlockers(0),
+      mCancelContentJSEpoch(0),
+      mWidgetNativeData(0) {
+  mozilla::HoldJSObjects(this);
+
+  nsWeakPtr weakPtrThis(do_GetWeakReference(
+      static_cast<nsIBrowserChild*>(this)));  // for capture by the lambda
+  mSetAllowedTouchBehaviorCallback =
+      [weakPtrThis](uint64_t aInputBlockId,
+                    const nsTArray<TouchBehaviorFlags>& aFlags) {
+        if (nsCOMPtr<nsIBrowserChild> browserChild =
+                do_QueryReferent(weakPtrThis)) {
+          static_cast<BrowserChild*>(browserChild.get())
+              ->SetAllowedTouchBehavior(aInputBlockId, aFlags);
+        }
+      };
+
+  // preloaded BrowserChild should not be added to child map
+  if (mUniqueId) {
+    MOZ_ASSERT(NestedBrowserChildMap().find(mUniqueId) ==
+               NestedBrowserChildMap().end());
+    NestedBrowserChildMap()[mUniqueId] = this;
+  }
+  mCoalesceMouseMoveEvents =
+      Preferences::GetBool("dom.event.coalesce_mouse_move");
+  if (mCoalesceMouseMoveEvents) {
+    mCoalescedMouseEventFlusher = new CoalescedMouseMoveFlusher(this);
+  }
+}
+
+const CompositorOptions& BrowserChild::GetCompositorOptions() const {
+  // If you're calling this before mCompositorOptions is set, well.. don't.
+  MOZ_ASSERT(mCompositorOptions);
+  return mCompositorOptions.ref();
+}
+
+bool BrowserChild::AsyncPanZoomEnabled() const {
+  // This might get called by the TouchEvent::PrefEnabled code before we have
+  // mCompositorOptions populated (bug 1370089). In that case we just assume
+  // APZ is enabled because we're in a content process (because BrowserChild)
+  // and APZ is probably going to be enabled here since e10s is enabled.
+  return mCompositorOptions ? mCompositorOptions->UseAPZ() : true;
+}
+
+NS_IMETHODIMP
+BrowserChild::Observe(nsISupports* aSubject, const char* aTopic,
+                      const char16_t* aData) {
+  if (!strcmp(aTopic, BEFORE_FIRST_PAINT)) {
+    if (AsyncPanZoomEnabled()) {
+      nsCOMPtr<Document> subject(do_QueryInterface(aSubject));
+      nsCOMPtr<Document> doc(GetTopLevelDocument());
+
+      if (subject == doc && doc->IsTopLevelContentDocument()) {
+        RefPtr<PresShell> presShell = doc->GetPresShell();
+        if (presShell) {
+          presShell->SetIsFirstPaint(true);
+        }
+
+        APZCCallbackHelper::InitializeRootDisplayport(presShell);
+      }
+    }
+  }
+
+  return NS_OK;
+}
+
+void BrowserChild::ContentReceivedInputBlock(uint64_t aInputBlockId,
+                                             bool aPreventDefault) const {
+  if (mApzcTreeManager) {
+    mApzcTreeManager->ContentReceivedInputBlock(aInputBlockId, aPreventDefault);
+  }
+}
+
+void BrowserChild::SetTargetAPZC(
+    uint64_t aInputBlockId,
+    const nsTArray<ScrollableLayerGuid>& aTargets) const {
+  if (mApzcTreeManager) {
+    mApzcTreeManager->SetTargetAPZC(aInputBlockId, aTargets);
+  }
+}
+
+void BrowserChild::SetAllowedTouchBehavior(
+    uint64_t aInputBlockId,
+    const nsTArray<TouchBehaviorFlags>& aTargets) const {
+  if (mApzcTreeManager) {
+    mApzcTreeManager->SetAllowedTouchBehavior(aInputBlockId, aTargets);
+  }
+}
+
+bool BrowserChild::DoUpdateZoomConstraints(
+    const uint32_t& aPresShellId, const ViewID& aViewId,
+    const Maybe<ZoomConstraints>& aConstraints) {
+  if (!mApzcTreeManager || mDestroyed) {
+    return false;
+  }
+
+  ScrollableLayerGuid guid =
+      ScrollableLayerGuid(mLayersId, aPresShellId, aViewId);
+
+  mApzcTreeManager->UpdateZoomConstraints(guid, aConstraints);
+  return true;
+}
+
+nsresult BrowserChild::Init(mozIDOMWindowProxy* aParent,
+                            WindowGlobalChild* aInitialWindowChild) {
+  MOZ_ASSERT_IF(aInitialWindowChild,
+                aInitialWindowChild->BrowsingContext() == mBrowsingContext);
+
+  nsCOMPtr<nsIWidget> widget = nsIWidget::CreatePuppetWidget(this);
+  mPuppetWidget = static_cast<PuppetWidget*>(widget.get());
+  if (!mPuppetWidget) {
+    NS_ERROR("couldn't create fake widget");
+    return NS_ERROR_FAILURE;
+  }
+  mPuppetWidget->InfallibleCreate(nullptr,
+                                  nullptr,  // no parents
+                                  LayoutDeviceIntRect(0, 0, 0, 0),
+                                  nullptr);  // HandleWidgetEvent
+
+  mWebBrowser = nsWebBrowser::Create(this, mPuppetWidget, mBrowsingContext,
+                                     aInitialWindowChild);
+  nsIWebBrowser* webBrowser = mWebBrowser;
+
+  mWebNav = do_QueryInterface(webBrowser);
+  NS_ASSERTION(mWebNav, "nsWebBrowser doesn't implement nsIWebNavigation?");
+
+  // Set the tab context attributes then pass to docShell
+  NotifyTabContextUpdated();
+
+  // IPC uses a WebBrowser object for which DNS prefetching is turned off
+  // by default. But here we really want it, so enable it explicitly
+  mWebBrowser->SetAllowDNSPrefetch(true);
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  MOZ_ASSERT(docShell);
+
+  mStatusFilter = new nsBrowserStatusFilter();
+
+  nsresult rv =
+      mStatusFilter->AddProgressListener(this, nsIWebProgress::NOTIFY_ALL);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  {
+    nsCOMPtr<nsIWebProgress> webProgress = do_QueryInterface(docShell);
+    rv = webProgress->AddProgressListener(mStatusFilter,
+                                          nsIWebProgress::NOTIFY_ALL);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+
+  docShell->SetAffectPrivateSessionLifetime(
+      mBrowsingContext->UsePrivateBrowsing() ||
+      mChromeFlags & nsIWebBrowserChrome::CHROME_PRIVATE_LIFETIME);
+
+#ifdef DEBUG
+  nsCOMPtr<nsILoadContext> loadContext = do_GetInterface(WebNavigation());
+  MOZ_ASSERT(loadContext);
+  MOZ_ASSERT(loadContext->UseRemoteTabs() ==
+             !!(mChromeFlags & nsIWebBrowserChrome::CHROME_REMOTE_WINDOW));
+  MOZ_ASSERT(loadContext->UseRemoteSubframes() ==
+             !!(mChromeFlags & nsIWebBrowserChrome::CHROME_FISSION_WINDOW));
+#endif  // defined(DEBUG)
+
+  // Few lines before, baseWindow->Create() will end up creating a new
+  // window root in nsGlobalWindow::SetDocShell.
+  // Then this chrome event handler, will be inherited to inner windows.
+  // We want to also set it to the docshell so that inner windows
+  // and any code that has access to the docshell
+  // can all listen to the same chrome event handler.
+  // XXX: ideally, we would set a chrome event handler earlier,
+  // and all windows, even the root one, will use the docshell one.
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+  NS_ENSURE_TRUE(window, NS_ERROR_FAILURE);
+  nsCOMPtr<EventTarget> chromeHandler = window->GetChromeEventHandler();
+  docShell->SetChromeEventHandler(chromeHandler);
+
+  if (window->GetCurrentInnerWindow()) {
+    window->SetKeyboardIndicators(ShowFocusRings());
+  } else {
+    // Skip ShouldShowFocusRing check if no inner window is available
+    window->SetInitialKeyboardIndicators(ShowFocusRings());
+  }
+
+  // Window scrollbar flags only affect top level remote frames, not fission
+  // frames.
+  if (mIsTopLevel) {
+    nsContentUtils::SetScrollbarsVisibility(
+        docShell, !!(mChromeFlags & nsIWebBrowserChrome::CHROME_SCROLLBARS));
+  }
+
+  nsWeakPtr weakPtrThis = do_GetWeakReference(
+      static_cast<nsIBrowserChild*>(this));  // for capture by the lambda
+  ContentReceivedInputBlockCallback callback(
+      [weakPtrThis](uint64_t aInputBlockId, bool aPreventDefault) {
+        if (nsCOMPtr<nsIBrowserChild> browserChild =
+                do_QueryReferent(weakPtrThis)) {
+          static_cast<BrowserChild*>(browserChild.get())
+              ->ContentReceivedInputBlock(aInputBlockId, aPreventDefault);
+        }
+      });
+  mAPZEventState = new APZEventState(mPuppetWidget, std::move(callback));
+
+  mIPCOpen = true;
+
+#if !defined(MOZ_WIDGET_ANDROID) && !defined(MOZ_THUNDERBIRD) && \
+    !defined(MOZ_SUITE)
+  mSessionStoreListener = new TabListener(docShell, nullptr);
+  rv = mSessionStoreListener->Init();
+  NS_ENSURE_SUCCESS(rv, rv);
+#endif
+
+  // We've all set up, make sure our visibility state is consistent. This is
+  // important for OOP iframes, which start off as hidden.
+  UpdateVisibility();
+
+  return NS_OK;
+}
+
+void BrowserChild::NotifyTabContextUpdated() {
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  MOZ_ASSERT(docShell);
+
+  if (!docShell) {
+    return;
+  }
+
+  // Set SANDBOXED_AUXILIARY_NAVIGATION flag if this is a receiver page.
+  if (!PresentationURL().IsEmpty()) {
+    // Return value of setting synced field should be checked. See bug 1656492.
+    Unused << mBrowsingContext->SetSandboxFlags(SANDBOXED_AUXILIARY_NAVIGATION);
+  }
+}
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(BrowserChild)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(BrowserChild)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBrowserChildMessageManager)
+  tmp->nsMessageManagerScriptExecutor::Unlink();
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWebBrowserChrome)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mStatusFilter)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mWebNav)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBrowsingContext)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_REFERENCE
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN(BrowserChild)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBrowserChildMessageManager)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWebBrowserChrome)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mStatusFilter)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mWebNav)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBrowsingContext)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_IMPL_CYCLE_COLLECTION_TRACE_BEGIN(BrowserChild)
+  tmp->nsMessageManagerScriptExecutor::Trace(aCallbacks, aClosure);
+NS_IMPL_CYCLE_COLLECTION_TRACE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(BrowserChild)
+  NS_INTERFACE_MAP_ENTRY(nsIWebBrowserChrome)
+  NS_INTERFACE_MAP_ENTRY(nsIEmbeddingSiteWindow)
+  NS_INTERFACE_MAP_ENTRY(nsIWebBrowserChromeFocus)
+  NS_INTERFACE_MAP_ENTRY(nsIInterfaceRequestor)
+  NS_INTERFACE_MAP_ENTRY(nsIWindowProvider)
+  NS_INTERFACE_MAP_ENTRY(nsIBrowserChild)
+  NS_INTERFACE_MAP_ENTRY(nsIObserver)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+  NS_INTERFACE_MAP_ENTRY(nsITooltipListener)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener)
+  NS_INTERFACE_MAP_ENTRY(nsIWebProgressListener2)
+  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIBrowserChild)
+NS_INTERFACE_MAP_END
+
+NS_IMPL_CYCLE_COLLECTING_ADDREF(BrowserChild)
+NS_IMPL_CYCLE_COLLECTING_RELEASE(BrowserChild)
+
+NS_IMETHODIMP
+BrowserChild::GetChromeFlags(uint32_t* aChromeFlags) {
+  *aChromeFlags = mChromeFlags;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetChromeFlags(uint32_t aChromeFlags) {
+  NS_WARNING("trying to SetChromeFlags from content process?");
+
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BrowserChild::RemoteSizeShellTo(int32_t aWidth, int32_t aHeight,
+                                int32_t aShellItemWidth,
+                                int32_t aShellItemHeight) {
+  nsCOMPtr<nsIDocShell> ourDocShell = do_GetInterface(WebNavigation());
+  nsCOMPtr<nsIBaseWindow> docShellAsWin(do_QueryInterface(ourDocShell));
+  NS_ENSURE_STATE(docShellAsWin);
+
+  int32_t width, height;
+  docShellAsWin->GetSize(&width, &height);
+
+  uint32_t flags = 0;
+  if (width == aWidth) {
+    flags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_CX;
+  }
+
+  if (height == aHeight) {
+    flags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_CY;
+  }
+
+  bool sent = SendSizeShellTo(flags, aWidth, aHeight, aShellItemWidth,
+                              aShellItemHeight);
+
+  return sent ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+BrowserChild::RemoteDropLinks(
+    const nsTArray<RefPtr<nsIDroppedLinkItem>>& aLinks) {
+  nsTArray<nsString> linksArray;
+  nsresult rv = NS_OK;
+  for (nsIDroppedLinkItem* link : aLinks) {
+    nsString tmp;
+    rv = link->GetUrl(tmp);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    linksArray.AppendElement(tmp);
+
+    rv = link->GetName(tmp);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    linksArray.AppendElement(tmp);
+
+    rv = link->GetType(tmp);
+    if (NS_FAILED(rv)) {
+      return rv;
+    }
+    linksArray.AppendElement(tmp);
+  }
+  bool sent = SendDropLinks(linksArray);
+
+  return sent ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+BrowserChild::ShowAsModal() {
+  NS_WARNING("BrowserChild::ShowAsModal not supported in BrowserChild");
+
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BrowserChild::IsWindowModal(bool* aRetVal) {
+  *aRetVal = false;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetLinkStatus(const nsAString& aStatusText) {
+  // We can only send the status after the ipc machinery is set up
+  if (IPCOpen()) {
+    SendSetLinkStatus(nsString(aStatusText));
+  }
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetDimensions(uint32_t aFlags, int32_t aX, int32_t aY,
+                            int32_t aCx, int32_t aCy) {
+  // The parent is in charge of the dimension changes. If JS code wants to
+  // change the dimensions (moveTo, screenX, etc.) we send a message to the
+  // parent about the new requested dimension, the parent does the resize/move
+  // then send a message to the child to update itself. For APIs like screenX
+  // this function is called with the current value for the non-changed values.
+  // In a series of calls like window.screenX = 10; window.screenY = 10; for
+  // the second call, since screenX is not yet updated we might accidentally
+  // reset back screenX to it's old value. To avoid this if a parameter did not
+  // change we want the parent to ignore its value.
+  int32_t x, y, cx, cy;
+  GetDimensions(aFlags, &x, &y, &cx, &cy);
+
+  if (x == aX) {
+    aFlags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_X;
+  }
+
+  if (y == aY) {
+    aFlags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_Y;
+  }
+
+  if (cx == aCx) {
+    aFlags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_CX;
+  }
+
+  if (cy == aCy) {
+    aFlags |= nsIEmbeddingSiteWindow::DIM_FLAGS_IGNORE_CY;
+  }
+
+  double scale = mPuppetWidget ? mPuppetWidget->GetDefaultScale().scale : 1.0;
+
+  Unused << SendSetDimensions(aFlags, aX, aY, aCx, aCy, scale);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetDimensions(uint32_t aFlags, int32_t* aX, int32_t* aY,
+                            int32_t* aCx, int32_t* aCy) {
+  ScreenIntRect rect = GetOuterRect();
+  if (aX) {
+    *aX = rect.x;
+  }
+  if (aY) {
+    *aY = rect.y;
+  }
+  if (aCx) {
+    *aCx = rect.width;
+  }
+  if (aCy) {
+    *aCy = rect.height;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetFocus() { return NS_ERROR_NOT_IMPLEMENTED; }
+
+NS_IMETHODIMP
+BrowserChild::GetVisibility(bool* aVisibility) {
+  *aVisibility = true;
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetVisibility(bool aVisibility) {
+  // should the platform support this? Bug 666365
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetTitle(nsAString& aTitle) {
+  NS_WARNING("BrowserChild::GetTitle not supported in BrowserChild");
+
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetTitle(const nsAString& aTitle) {
+  // JavaScript sends the "DOMTitleChanged" event to the parent
+  // via the message manager.
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetSiteWindow(void** aSiteWindow) {
+  NS_WARNING("BrowserChild::GetSiteWindow not supported in BrowserChild");
+
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP
+BrowserChild::Blur() { return NS_ERROR_NOT_IMPLEMENTED; }
+
+NS_IMETHODIMP
+BrowserChild::FocusNextElement(bool aForDocumentNavigation) {
+  SendMoveFocus(true, aForDocumentNavigation);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::FocusPrevElement(bool aForDocumentNavigation) {
+  SendMoveFocus(false, aForDocumentNavigation);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetInterface(const nsIID& aIID, void** aSink) {
+  if (aIID.Equals(NS_GET_IID(nsIWebBrowserChrome3))) {
+    return GetWebBrowserChrome(reinterpret_cast<nsIWebBrowserChrome3**>(aSink));
+  }
+
+  // XXXbz should we restrict the set of interfaces we hand out here?
+  // See bug 537429
+  return QueryInterface(aIID, aSink);
+}
+
+NS_IMETHODIMP
+BrowserChild::ProvideWindow(nsIOpenWindowInfo* aOpenWindowInfo,
+                            uint32_t aChromeFlags, bool aCalledFromJS,
+                            bool aWidthSpecified, nsIURI* aURI,
+                            const nsAString& aName, const nsACString& aFeatures,
+                            bool aForceNoOpener, bool aForceNoReferrer,
+                            nsDocShellLoadState* aLoadState, bool* aWindowIsNew,
+                            BrowsingContext** aReturn) {
+  *aReturn = nullptr;
+
+  RefPtr<BrowsingContext> parent = aOpenWindowInfo->GetParent();
+
+  int32_t openLocation = nsWindowWatcher::GetWindowOpenLocation(
+      parent->GetDOMWindow(), aChromeFlags, aCalledFromJS, aWidthSpecified,
+      aOpenWindowInfo->GetIsForPrinting());
+
+  // If it turns out we're opening in the current browser, just hand over the
+  // current browser's docshell.
+  if (openLocation == nsIBrowserDOMWindow::OPEN_CURRENTWINDOW) {
+    nsCOMPtr<nsIWebBrowser> browser = do_GetInterface(WebNavigation());
+    *aWindowIsNew = false;
+
+    nsCOMPtr<mozIDOMWindowProxy> win;
+    MOZ_TRY(browser->GetContentDOMWindow(getter_AddRefs(win)));
+
+    RefPtr<BrowsingContext> bc(
+        nsPIDOMWindowOuter::From(win)->GetBrowsingContext());
+    bc.forget(aReturn);
+    return NS_OK;
+  }
+
+  // Note that ProvideWindowCommon may return NS_ERROR_ABORT if the
+  // open window call was canceled.  It's important that we pass this error
+  // code back to our caller.
+  ContentChild* cc = ContentChild::GetSingleton();
+  return cc->ProvideWindowCommon(this, aOpenWindowInfo, aChromeFlags,
+                                 aCalledFromJS, aWidthSpecified, aURI, aName,
+                                 aFeatures, aForceNoOpener, aForceNoReferrer,
+                                 aLoadState, aWindowIsNew, aReturn);
+}
+
+void BrowserChild::DestroyWindow() {
+  mBrowsingContext = nullptr;
+
+  if (mStatusFilter) {
+    if (nsCOMPtr<nsIWebProgress> webProgress =
+            do_QueryInterface(WebNavigation())) {
+      webProgress->RemoveProgressListener(mStatusFilter);
+    }
+
+    mStatusFilter->RemoveProgressListener(this);
+    mStatusFilter = nullptr;
+  }
+
+  if (mCoalescedMouseEventFlusher) {
+    mCoalescedMouseEventFlusher->RemoveObserver();
+    mCoalescedMouseEventFlusher = nullptr;
+  }
+
+  if (mSessionStoreListener) {
+    mSessionStoreListener->RemoveListeners();
+    mSessionStoreListener = nullptr;
+  }
+
+  // In case we don't have chance to process all entries, clean all data in
+  // the queue.
+  while (mToBeDispatchedMouseData.GetSize() > 0) {
+    UniquePtr<CoalescedMouseData> data(
+        static_cast<CoalescedMouseData*>(mToBeDispatchedMouseData.PopFront()));
+    data.reset();
+  }
+
+  nsCOMPtr<nsIBaseWindow> baseWindow = do_QueryInterface(WebNavigation());
+  if (baseWindow) baseWindow->Destroy();
+
+  if (mPuppetWidget) {
+    mPuppetWidget->Destroy();
+  }
+
+  mLayersConnected = Nothing();
+
+  if (mLayersId.IsValid()) {
+    StaticMutexAutoLock lock(sBrowserChildrenMutex);
+
+    MOZ_ASSERT(sBrowserChildren);
+    sBrowserChildren->Remove(uint64_t(mLayersId));
+    if (!sBrowserChildren->Count()) {
+      delete sBrowserChildren;
+      sBrowserChildren = nullptr;
+    }
+    mLayersId = layers::LayersId{0};
+  }
+}
+
+void BrowserChild::ActorDestroy(ActorDestroyReason why) {
+  mIPCOpen = false;
+
+  DestroyWindow();
+
+  if (mBrowserChildMessageManager) {
+    // We should have a message manager if the global is alive, but it
+    // seems sometimes we don't.  Assert in aurora/nightly, but don't
+    // crash in release builds.
+    MOZ_DIAGNOSTIC_ASSERT(mBrowserChildMessageManager->GetMessageManager());
+    if (mBrowserChildMessageManager->GetMessageManager()) {
+      // The messageManager relays messages via the BrowserChild which
+      // no longer exists.
+      mBrowserChildMessageManager->DisconnectMessageManager();
+    }
+  }
+
+  CompositorBridgeChild* compositorChild = CompositorBridgeChild::Get();
+  if (compositorChild) {
+    compositorChild->CancelNotifyAfterRemotePaint(this);
+  }
+
+  if (GetTabId() != 0) {
+    NestedBrowserChildMap().erase(GetTabId());
+  }
+}
+
+BrowserChild::~BrowserChild() {
+  mAnonymousGlobalScopes.Clear();
+
+  DestroyWindow();
+
+  nsCOMPtr<nsIWebBrowser> webBrowser = do_QueryInterface(WebNavigation());
+  if (webBrowser) {
+    webBrowser->SetContainerWindow(nullptr);
+  }
+
+  mozilla::DropJSObjects(this);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvWillChangeProcess(
+    WillChangeProcessResolver&& aResolve) {
+  if (mWebBrowser) {
+    mWebBrowser->SetWillChangeProcess();
+  }
+  aResolve(true);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvLoadURL(
+    nsDocShellLoadState* aLoadState, const ParentShowInfo& aInfo) {
+  if (!mDidLoadURLInit) {
+    mDidLoadURLInit = true;
+    if (!InitBrowserChildMessageManager()) {
+      return IPC_FAIL_NO_REASON(this);
+    }
+
+    ApplyParentShowInfo(aInfo);
+  }
+  nsAutoCString spec;
+  aLoadState->URI()->GetSpec(spec);
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  MOZ_ASSERT(docShell);
+  if (!docShell) {
+    NS_WARNING("WebNavigation does not have a docshell");
+    return IPC_OK();
+  }
+  docShell->LoadURI(aLoadState, true);
+
+  nsDocShell::Cast(docShell)->MaybeClearStorageAccessFlag();
+
+  CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::URL, spec);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvResumeLoad(
+    const uint64_t& aPendingSwitchID, const ParentShowInfo& aInfo) {
+  if (!mDidLoadURLInit) {
+    mDidLoadURLInit = true;
+    if (!InitBrowserChildMessageManager()) {
+      return IPC_FAIL_NO_REASON(this);
+    }
+
+    ApplyParentShowInfo(aInfo);
+  }
+
+  nsresult rv = WebNavigation()->ResumeRedirectedLoad(aPendingSwitchID, -1);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("WebNavigation()->ResumeRedirectedLoad failed");
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvCloneDocumentTreeIntoSelf(
+    const MaybeDiscarded<BrowsingContext>& aSourceBC) {
+  if (NS_WARN_IF(aSourceBC.IsNullOrDiscarded())) {
+    return IPC_OK();
+  }
+  nsCOMPtr<Document> sourceDocument = aSourceBC.get()->GetDocument();
+  if (NS_WARN_IF(!sourceDocument)) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIDocShell> ourDocShell = do_GetInterface(WebNavigation());
+  if (NS_WARN_IF(!ourDocShell)) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIContentViewer> cv;
+  ourDocShell->GetContentViewer(getter_AddRefs(cv));
+  if (NS_WARN_IF(!cv)) {
+    return IPC_OK();
+  }
+
+  RefPtr<Document> clone;
+  {
+    AutoPrintEventDispatcher dispatcher(*sourceDocument);
+    nsAutoScriptBlocker scriptBlocker;
+    bool hasInProcessCallbacks = false;
+    clone = sourceDocument->CreateStaticClone(ourDocShell, cv,
+                                              &hasInProcessCallbacks);
+    if (NS_WARN_IF(!clone)) {
+      return IPC_OK();
+    }
+  }
+
+  // Since the clone document is not parsed-created, we need to initialize
+  // layout manually. This is usually done in ReflowPrintObject for non-remote
+  // documents.
+  if (RefPtr<PresShell> ps = clone->GetPresShell()) {
+    if (!ps->DidInitialize()) {
+      nsresult rv = ps->Initialize();
+      Unused << NS_WARN_IF(NS_FAILED(rv));
+    }
+  }
+
+  return IPC_OK();
+}
+
+void BrowserChild::DoFakeShow(const ParentShowInfo& aParentShowInfo) {
+  OwnerShowInfo ownerInfo{ScreenIntSize(), ScrollbarPreference::Auto,
+                          nsSizeMode_Normal};
+  RecvShow(aParentShowInfo, ownerInfo);
+  mDidFakeShow = true;
+}
+
+void BrowserChild::ApplyParentShowInfo(const ParentShowInfo& aInfo) {
+  // Even if we already set real show info, the dpi / rounding & scale may still
+  // be invalid (if BrowserParent wasn't able to get widget it would just send
+  // 0). So better to always set up-to-date values here.
+  if (aInfo.dpi() > 0) {
+    mPuppetWidget->UpdateBackingScaleCache(aInfo.dpi(), aInfo.widgetRounding(),
+                                           aInfo.defaultScale());
+  }
+
+  if (mDidSetRealShowInfo) {
+    return;
+  }
+
+  if (!aInfo.fakeShowInfo()) {
+    // Once we've got one ShowInfo from parent, no need to update the values
+    // anymore.
+    mDidSetRealShowInfo = true;
+  }
+
+  mIsTransparent = aInfo.isTransparent();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvShow(
+    const ParentShowInfo& aParentInfo, const OwnerShowInfo& aOwnerInfo) {
+  bool res = true;
+
+  mPuppetWidget->SetSizeMode(aOwnerInfo.sizeMode());
+  if (!mDidFakeShow) {
+    nsCOMPtr<nsIBaseWindow> baseWindow = do_QueryInterface(WebNavigation());
+    if (!baseWindow) {
+      NS_ERROR("WebNavigation() doesn't QI to nsIBaseWindow");
+      return IPC_FAIL_NO_REASON(this);
+    }
+
+    baseWindow->SetVisibility(true);
+    res = InitBrowserChildMessageManager();
+  }
+
+  ApplyParentShowInfo(aParentInfo);
+
+  if (!mIsTopLevel) {
+    RecvScrollbarPreferenceChanged(aOwnerInfo.scrollbarPreference());
+  }
+
+  if (!res) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+
+  UpdateVisibility();
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvInitRendering(
+    const TextureFactoryIdentifier& aTextureFactoryIdentifier,
+    const layers::LayersId& aLayersId,
+    const CompositorOptions& aCompositorOptions, const bool& aLayersConnected) {
+  mLayersConnected = Some(aLayersConnected);
+  InitRenderingState(aTextureFactoryIdentifier, aLayersId, aCompositorOptions);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvScrollbarPreferenceChanged(
+    ScrollbarPreference aPreference) {
+  MOZ_ASSERT(!mIsTopLevel,
+             "Scrollbar visibility should be derived from chrome flags for "
+             "top-level windows");
+  if (nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation())) {
+    nsDocShell::Cast(docShell)->SetScrollbarPreference(aPreference);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvCompositorOptionsChanged(
+    const CompositorOptions& aNewOptions) {
+  MOZ_ASSERT(mCompositorOptions);
+
+  // The only compositor option we currently support changing is APZ
+  // enablement. Even that is only partially supported for now:
+  //   * Going from APZ to non-APZ is fine - we just flip the stored flag.
+  //     Note that we keep the actors (mApzcTreeManager, and the APZChild
+  //     created in InitAPZState()) around (read on for why).
+  //   * Going from non-APZ to APZ is only supported if we were using
+  //     APZ initially (at InitRendering() time) and we are transitioning
+  //     back. In this case, we just reuse the actors which we kept around.
+  //     Fully supporting a non-APZ to APZ transition (i.e. even in cases
+  //     where we initialized as non-APZ) would require setting up the actors
+  //     here. (In that case, we would also have the options of destroying
+  //     the actors in the APZ --> non-APZ case, and always re-creating them
+  //     during a non-APZ --> APZ transition).
+  mCompositorOptions->SetUseAPZ(aNewOptions.UseAPZ());
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvUpdateDimensions(
+    const DimensionInfo& aDimensionInfo) {
+  if (mLayersConnected.isNothing()) {
+    return IPC_OK();
+  }
+
+  mUnscaledOuterRect = aDimensionInfo.rect();
+  mClientOffset = aDimensionInfo.clientOffset();
+  mChromeOffset = aDimensionInfo.chromeOffset();
+  MOZ_ASSERT_IF(!IsTopLevel(), mChromeOffset == LayoutDeviceIntPoint());
+
+  mOrientation = aDimensionInfo.orientation();
+  SetUnscaledInnerSize(aDimensionInfo.size());
+  if (!mHasValidInnerSize && aDimensionInfo.size().width != 0 &&
+      aDimensionInfo.size().height != 0) {
+    mHasValidInnerSize = true;
+  }
+
+  ScreenIntSize screenSize = GetInnerSize();
+  ScreenIntRect screenRect = GetOuterRect();
+
+  // Make sure to set the size on the document viewer first.  The
+  // MobileViewportManager needs the content viewer size to be updated before
+  // the reflow, otherwise it gets a stale size when it computes a new CSS
+  // viewport.
+  nsCOMPtr<nsIBaseWindow> baseWin = do_QueryInterface(WebNavigation());
+  baseWin->SetPositionAndSize(0, 0, screenSize.width, screenSize.height,
+                              nsIBaseWindow::eRepaint);
+
+  mPuppetWidget->Resize(screenRect.x + mClientOffset.x + mChromeOffset.x,
+                        screenRect.y + mClientOffset.y + mChromeOffset.y,
+                        screenSize.width, screenSize.height, true);
+
+  RecvSafeAreaInsetsChanged(mPuppetWidget->GetSafeAreaInsets());
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSizeModeChanged(
+    const nsSizeMode& aSizeMode) {
+  mPuppetWidget->SetSizeMode(aSizeMode);
+  if (!mPuppetWidget->IsVisible()) {
+    return IPC_OK();
+  }
+  nsCOMPtr<Document> document(GetTopLevelDocument());
+  if (!document) {
+    return IPC_OK();
+  }
+  nsPresContext* presContext = document->GetPresContext();
+  if (presContext) {
+    presContext->SizeModeChanged(aSizeMode);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvChildToParentMatrix(
+    const Maybe<gfx::Matrix4x4>& aMatrix,
+    const ScreenRect& aTopLevelViewportVisibleRectInBrowserCoords) {
+  mChildToParentConversionMatrix =
+      LayoutDeviceToLayoutDeviceMatrix4x4::FromUnknownMatrix(aMatrix);
+  mTopLevelViewportVisibleRectInBrowserCoords =
+      aTopLevelViewportVisibleRectInBrowserCoords;
+
+  // Trigger an intersection observation update since ancestor viewports
+  // changed.
+  if (RefPtr<Document> toplevelDoc = GetTopLevelDocument()) {
+    if (nsPresContext* pc = toplevelDoc->GetPresContext()) {
+      pc->RefreshDriver()->EnsureIntersectionObservationsUpdateHappens();
+    }
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSetIsUnderHiddenEmbedderElement(
+    const bool& aIsUnderHiddenEmbedderElement) {
+  if (RefPtr<PresShell> presShell = GetTopLevelPresShell()) {
+    presShell->SetIsUnderHiddenEmbedderElement(aIsUnderHiddenEmbedderElement);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvDynamicToolbarMaxHeightChanged(
+    const ScreenIntCoord& aHeight) {
+#if defined(MOZ_WIDGET_ANDROID)
+  mDynamicToolbarMaxHeight = aHeight;
+
+  RefPtr<Document> document = GetTopLevelDocument();
+  if (!document) {
+    return IPC_OK();
+  }
+
+  if (RefPtr<nsPresContext> presContext = document->GetPresContext()) {
+    presContext->SetDynamicToolbarMaxHeight(aHeight);
+  }
+#endif
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvDynamicToolbarOffsetChanged(
+    const ScreenIntCoord& aOffset) {
+#if defined(MOZ_WIDGET_ANDROID)
+  RefPtr<Document> document = GetTopLevelDocument();
+  if (!document) {
+    return IPC_OK();
+  }
+
+  if (nsPresContext* presContext = document->GetPresContext()) {
+    presContext->UpdateDynamicToolbarOffset(aOffset);
+  }
+#endif
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSuppressDisplayport(
+    const bool& aEnabled) {
+  if (RefPtr<PresShell> presShell = GetTopLevelPresShell()) {
+    presShell->SuppressDisplayport(aEnabled);
+  }
+  return IPC_OK();
+}
+
+void BrowserChild::HandleDoubleTap(const CSSPoint& aPoint,
+                                   const Modifiers& aModifiers,
+                                   const ScrollableLayerGuid& aGuid) {
+  MOZ_LOG(
+      sApzChildLog, LogLevel::Debug,
+      ("Handling double tap at %s with %p %p\n", ToString(aPoint).c_str(),
+       mBrowserChildMessageManager ? mBrowserChildMessageManager->GetWrapper()
+                                   : nullptr,
+       mBrowserChildMessageManager.get()));
+
+  if (!mBrowserChildMessageManager) {
+    return;
+  }
+
+  // Note: there is nothing to do with the modifiers here, as we are not
+  // synthesizing any sort of mouse event.
+  RefPtr<Document> document = GetTopLevelDocument();
+  CSSRect zoomToRect = CalculateRectToZoomTo(document, aPoint);
+  // The double-tap can be dispatched by any scroll frame (so |aGuid| could be
+  // the guid of any scroll frame), but the zoom-to-rect operation must be
+  // performed by the root content scroll frame, so query its identifiers
+  // for the SendZoomToRect() call rather than using the ones from |aGuid|.
+  uint32_t presShellId;
+  ViewID viewId;
+  if (APZCCallbackHelper::GetOrCreateScrollIdentifiers(
+          document->GetDocumentElement(), &presShellId, &viewId) &&
+      mApzcTreeManager) {
+    ScrollableLayerGuid guid(mLayersId, presShellId, viewId);
+
+    mApzcTreeManager->ZoomToRect(guid, zoomToRect, DEFAULT_BEHAVIOR);
+  }
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvHandleTap(
+    const GeckoContentController::TapType& aType,
+    const LayoutDevicePoint& aPoint, const Modifiers& aModifiers,
+    const ScrollableLayerGuid& aGuid, const uint64_t& aInputBlockId) {
+  // IPDL doesn't hold a strong reference to protocols as they're not required
+  // to be refcounted. This function can run script, which may trigger a nested
+  // event loop, which may release this, so we hold a strong reference here.
+  RefPtr<BrowserChild> kungFuDeathGrip(this);
+  RefPtr<PresShell> presShell = GetTopLevelPresShell();
+  if (!presShell) {
+    return IPC_OK();
+  }
+  if (!presShell->GetPresContext()) {
+    return IPC_OK();
+  }
+  CSSToLayoutDeviceScale scale(
+      presShell->GetPresContext()->CSSToDevPixelScale());
+  CSSPoint point = aPoint / scale;
+
+  // Stash the guid in InputAPZContext so that when the visual-to-layout
+  // transform is applied to the event's coordinates, we use the right transform
+  // based on the scroll frame being targeted.
+  // The other values don't really matter.
+  InputAPZContext context(aGuid, aInputBlockId, nsEventStatus_eSentinel);
+
+  switch (aType) {
+    case GeckoContentController::TapType::eSingleTap:
+      if (mBrowserChildMessageManager) {
+        mAPZEventState->ProcessSingleTap(point, scale, aModifiers, 1);
+      }
+      break;
+    case GeckoContentController::TapType::eDoubleTap:
+      HandleDoubleTap(point, aModifiers, aGuid);
+      break;
+    case GeckoContentController::TapType::eSecondTap:
+      if (mBrowserChildMessageManager) {
+        mAPZEventState->ProcessSingleTap(point, scale, aModifiers, 2);
+      }
+      break;
+    case GeckoContentController::TapType::eLongTap:
+      if (mBrowserChildMessageManager) {
+        RefPtr<APZEventState> eventState(mAPZEventState);
+        eventState->ProcessLongTap(presShell, point, scale, aModifiers,
+                                   aInputBlockId);
+      }
+      break;
+    case GeckoContentController::TapType::eLongTapUp:
+      if (mBrowserChildMessageManager) {
+        RefPtr<APZEventState> eventState(mAPZEventState);
+        eventState->ProcessLongTapUp(presShell, point, scale, aModifiers);
+      }
+      break;
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityHandleTap(
+    const GeckoContentController::TapType& aType,
+    const LayoutDevicePoint& aPoint, const Modifiers& aModifiers,
+    const ScrollableLayerGuid& aGuid, const uint64_t& aInputBlockId) {
+  // IPDL doesn't hold a strong reference to protocols as they're not required
+  // to be refcounted. This function can run script, which may trigger a nested
+  // event loop, which may release this, so we hold a strong reference here.
+  RefPtr<BrowserChild> kungFuDeathGrip(this);
+  return RecvHandleTap(aType, aPoint, aModifiers, aGuid, aInputBlockId);
+}
+
+bool BrowserChild::NotifyAPZStateChange(
+    const ViewID& aViewId,
+    const layers::GeckoContentController::APZStateChange& aChange,
+    const int& aArg) {
+  mAPZEventState->ProcessAPZStateChange(aViewId, aChange, aArg);
+  if (aChange ==
+      layers::GeckoContentController::APZStateChange::eTransformEnd) {
+    // This is used by tests to determine when the APZ is done doing whatever
+    // it's doing. XXX generify this as needed when writing additional tests.
+    nsCOMPtr<nsIObserverService> observerService =
+        mozilla::services::GetObserverService();
+    observerService->NotifyObservers(nullptr, "APZ:TransformEnd", nullptr);
+  }
+  return true;
+}
+
+void BrowserChild::StartScrollbarDrag(
+    const layers::AsyncDragMetrics& aDragMetrics) {
+  ScrollableLayerGuid guid(mLayersId, aDragMetrics.mPresShellId,
+                           aDragMetrics.mViewId);
+
+  if (mApzcTreeManager) {
+    mApzcTreeManager->StartScrollbarDrag(guid, aDragMetrics);
+  }
+}
+
+void BrowserChild::ZoomToRect(const uint32_t& aPresShellId,
+                              const ScrollableLayerGuid::ViewID& aViewId,
+                              const CSSRect& aRect, const uint32_t& aFlags) {
+  ScrollableLayerGuid guid(mLayersId, aPresShellId, aViewId);
+
+  if (mApzcTreeManager) {
+    mApzcTreeManager->ZoomToRect(guid, aRect, aFlags);
+  }
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvActivate(uint64_t aActionId) {
+  MOZ_ASSERT(mWebBrowser);
+  mWebBrowser->FocusActivate(aActionId);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvDeactivate(uint64_t aActionId) {
+  MOZ_ASSERT(mWebBrowser);
+  mWebBrowser->FocusDeactivate(aActionId);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSetKeyboardIndicators(
+    const UIStateChangeType& aShowFocusRings) {
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+  NS_ENSURE_TRUE(window, IPC_OK());
+  window->SetKeyboardIndicators(aShowFocusRings);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvStopIMEStateManagement() {
+  IMEStateManager::StopIMEStateManagement();
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvMouseEvent(
+    const nsString& aType, const float& aX, const float& aY,
+    const int32_t& aButton, const int32_t& aClickCount,
+    const int32_t& aModifiers) {
+  // IPDL doesn't hold a strong reference to protocols as they're not required
+  // to be refcounted. This function can run script, which may trigger a nested
+  // event loop, which may release this, so we hold a strong reference here.
+  RefPtr<BrowserChild> kungFuDeathGrip(this);
+  RefPtr<PresShell> presShell = GetTopLevelPresShell();
+  APZCCallbackHelper::DispatchMouseEvent(presShell, aType, CSSPoint(aX, aY),
+                                         aButton, aClickCount, aModifiers,
+                                         MouseEvent_Binding::MOZ_SOURCE_UNKNOWN,
+                                         0 /* Use the default value here. */);
+  return IPC_OK();
+}
+
+void BrowserChild::ProcessPendingCoalescedMouseDataAndDispatchEvents() {
+  if (!mCoalesceMouseMoveEvents || !mCoalescedMouseEventFlusher) {
+    // We don't enable mouse coalescing or we are destroying BrowserChild.
+    return;
+  }
+
+  // We may reentry the event loop and push more data to
+  // mToBeDispatchedMouseData while dispatching an event.
+
+  // We may have some pending coalesced data while dispatch an event and reentry
+  // the event loop. In that case we don't have chance to consume the remainding
+  // pending data until we get new mouse events. Get some helps from
+  // mCoalescedMouseEventFlusher to trigger it.
+  mCoalescedMouseEventFlusher->StartObserver();
+
+  while (mToBeDispatchedMouseData.GetSize() > 0) {
+    UniquePtr<CoalescedMouseData> data(
+        static_cast<CoalescedMouseData*>(mToBeDispatchedMouseData.PopFront()));
+
+    UniquePtr<WidgetMouseEvent> event = data->TakeCoalescedEvent();
+    if (event) {
+      // Dispatch the pending events. Using HandleRealMouseButtonEvent
+      // to bypass the coalesce handling in RecvRealMouseMoveEvent. Can't use
+      // RecvRealMouseButtonEvent because we may also put some mouse events
+      // other than mousemove.
+      HandleRealMouseButtonEvent(*event, data->GetScrollableLayerGuid(),
+                                 data->GetInputBlockId());
+    }
+  }
+  // mCoalescedMouseEventFlusher may be destroyed when reentrying the event
+  // loop.
+  if (mCoalescedMouseEventFlusher) {
+    mCoalescedMouseEventFlusher->RemoveObserver();
+  }
+}
+
+LayoutDeviceToLayoutDeviceMatrix4x4
+BrowserChild::GetChildToParentConversionMatrix() const {
+  if (mChildToParentConversionMatrix) {
+    return *mChildToParentConversionMatrix;
+  }
+  LayoutDevicePoint offset(GetChromeOffset());
+  return LayoutDeviceToLayoutDeviceMatrix4x4::Translation(offset);
+}
+
+ScreenRect BrowserChild::GetTopLevelViewportVisibleRectInBrowserCoords() const {
+  return mTopLevelViewportVisibleRectInBrowserCoords;
+}
+
+void BrowserChild::FlushAllCoalescedMouseData() {
+  MOZ_ASSERT(mCoalesceMouseMoveEvents);
+
+  // Move all entries from mCoalescedMouseData to mToBeDispatchedMouseData.
+  for (auto iter = mCoalescedMouseData.Iter(); !iter.Done(); iter.Next()) {
+    CoalescedMouseData* data = iter.UserData();
+    if (!data || data->IsEmpty()) {
+      continue;
+    }
+    UniquePtr<CoalescedMouseData> dispatchData =
+        MakeUnique<CoalescedMouseData>();
+
+    dispatchData->RetrieveDataFrom(*data);
+    mToBeDispatchedMouseData.Push(dispatchData.release());
+  }
+  mCoalescedMouseData.Clear();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealMouseMoveEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  if (mCoalesceMouseMoveEvents && mCoalescedMouseEventFlusher) {
+    CoalescedMouseData* data =
+        mCoalescedMouseData.LookupOrAdd(aEvent.pointerId);
+    MOZ_ASSERT(data);
+    if (data->CanCoalesce(aEvent, aGuid, aInputBlockId)) {
+      data->Coalesce(aEvent, aGuid, aInputBlockId);
+      mCoalescedMouseEventFlusher->StartObserver();
+      return IPC_OK();
+    }
+    // Can't coalesce current mousemove event. Put the coalesced mousemove data
+    // with the same pointer id to mToBeDispatchedMouseData, coalesce the
+    // current one, and process all pending data in mToBeDispatchedMouseData.
+    UniquePtr<CoalescedMouseData> dispatchData =
+        MakeUnique<CoalescedMouseData>();
+
+    dispatchData->RetrieveDataFrom(*data);
+    mToBeDispatchedMouseData.Push(dispatchData.release());
+
+    // Put new data to replace the old one in the hash table.
+    CoalescedMouseData* newData = new CoalescedMouseData();
+    mCoalescedMouseData.Put(aEvent.pointerId, newData);
+    newData->Coalesce(aEvent, aGuid, aInputBlockId);
+
+    // Dispatch all pending mouse events.
+    ProcessPendingCoalescedMouseDataAndDispatchEvents();
+    mCoalescedMouseEventFlusher->StartObserver();
+  } else if (!RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealMouseMoveEventForTests(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseMoveEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealMouseMoveEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseMoveEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult
+BrowserChild::RecvNormalPriorityRealMouseMoveEventForTests(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseMoveEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSynthMouseMoveEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  if (!RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPrioritySynthMouseMoveEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvSynthMouseMoveEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealMouseButtonEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  if (mCoalesceMouseMoveEvents && mCoalescedMouseEventFlusher &&
+      aEvent.mMessage != eMouseMove) {
+    // When receiving a mouse event other than mousemove, we have to dispatch
+    // all coalesced events before it. However, we can't dispatch all pending
+    // coalesced events directly because we may reentry the event loop while
+    // dispatching. To make sure we won't dispatch disorder events, we move all
+    // coalesced mousemove events and current event to a deque to dispatch them.
+    // When reentrying the event loop and dispatching more events, we put new
+    // events in the end of the nsQueue and dispatch events from the beginning.
+    FlushAllCoalescedMouseData();
+
+    UniquePtr<CoalescedMouseData> dispatchData =
+        MakeUnique<CoalescedMouseData>();
+
+    dispatchData->Coalesce(aEvent, aGuid, aInputBlockId);
+    mToBeDispatchedMouseData.Push(dispatchData.release());
+
+    ProcessPendingCoalescedMouseDataAndDispatchEvents();
+    return IPC_OK();
+  }
+  HandleRealMouseButtonEvent(aEvent, aGuid, aInputBlockId);
+  return IPC_OK();
+}
+
+void BrowserChild::HandleRealMouseButtonEvent(const WidgetMouseEvent& aEvent,
+                                              const ScrollableLayerGuid& aGuid,
+                                              const uint64_t& aInputBlockId) {
+  WidgetMouseEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+
+  // We need one InputAPZContext here to propagate |aGuid| to places in
+  // SendSetTargetAPZCNotification() which apply the visual-to-layout transform,
+  // and another below to propagate the |postLayerization| flag (whose value
+  // we don't know until SendSetTargetAPZCNotification() returns) into
+  // the event dispatch code.
+  InputAPZContext context1(aGuid, aInputBlockId, nsEventStatus_eSentinel);
+
+  // Mouse events like eMouseEnterIntoWidget, that are created in the parent
+  // process EventStateManager code, have an input block id which they get from
+  // the InputAPZContext in the parent process stack. However, they did not
+  // actually go through the APZ code and so their mHandledByAPZ flag is false.
+  // Since thos events didn't go through APZ, we don't need to send
+  // notifications for them.
+  UniquePtr<DisplayportSetListener> postLayerization;
+  if (aInputBlockId && localEvent.mFlags.mHandledByAPZ) {
+    nsCOMPtr<Document> document(GetTopLevelDocument());
+    postLayerization = APZCCallbackHelper::SendSetTargetAPZCNotification(
+        mPuppetWidget, document, localEvent, aGuid.mLayersId, aInputBlockId);
+  }
+
+  InputAPZContext context2(aGuid, aInputBlockId, nsEventStatus_eSentinel,
+                           postLayerization != nullptr);
+
+  DispatchWidgetEventViaAPZ(localEvent);
+
+  if (aInputBlockId && localEvent.mFlags.mHandledByAPZ) {
+    mAPZEventState->ProcessMouseEvent(localEvent, aInputBlockId);
+  }
+
+  // Do this after the DispatchWidgetEventViaAPZ call above, so that if the
+  // mouse event triggered a post-refresh AsyncDragMetrics message to be sent
+  // to APZ (from scrollbar dragging in nsSliderFrame), then that will reach
+  // APZ before the SetTargetAPZC message. This ensures the drag input block
+  // gets the drag metrics before handling the input events.
+  if (postLayerization && postLayerization->Register()) {
+    Unused << postLayerization.release();
+  }
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealMouseButtonEvent(
+    const WidgetMouseEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvRealMouseButtonEvent(aEvent, aGuid, aInputBlockId);
+}
+
+// In case handling repeated mouse wheel takes much time, we skip firing current
+// wheel event if it may be coalesced to the next one.
+bool BrowserChild::MaybeCoalesceWheelEvent(const WidgetWheelEvent& aEvent,
+                                           const ScrollableLayerGuid& aGuid,
+                                           const uint64_t& aInputBlockId,
+                                           bool* aIsNextWheelEvent) {
+  MOZ_ASSERT(aIsNextWheelEvent);
+  if (aEvent.mMessage == eWheel) {
+    GetIPCChannel()->PeekMessages(
+        [aIsNextWheelEvent](const IPC::Message& aMsg) -> bool {
+          if (aMsg.type() == mozilla::dom::PBrowser::Msg_MouseWheelEvent__ID) {
+            *aIsNextWheelEvent = true;
+          }
+          return false;  // Stop peeking.
+        });
+    // We only coalesce the current event when
+    // 1. It's eWheel (we don't coalesce eOperationStart and eWheelOperationEnd)
+    // 2. It's not the first wheel event.
+    // 3. It's not the last wheel event.
+    // 4. It's dispatched before the last wheel event was processed +
+    //    the processing time of the last event.
+    //    This way pages spending lots of time in wheel listeners get wheel
+    //    events coalesced more aggressively.
+    // 5. It has same attributes as the coalesced wheel event which is not yet
+    //    fired.
+    if (!mLastWheelProcessedTimeFromParent.IsNull() && *aIsNextWheelEvent &&
+        aEvent.mTimeStamp < (mLastWheelProcessedTimeFromParent +
+                             mLastWheelProcessingDuration) &&
+        (mCoalescedWheelData.IsEmpty() ||
+         mCoalescedWheelData.CanCoalesce(aEvent, aGuid, aInputBlockId))) {
+      mCoalescedWheelData.Coalesce(aEvent, aGuid, aInputBlockId);
+      return true;
+    }
+  }
+  return false;
+}
+
+nsEventStatus BrowserChild::DispatchWidgetEventViaAPZ(WidgetGUIEvent& aEvent) {
+  aEvent.ResetWaitingReplyFromRemoteProcessState();
+  return APZCCallbackHelper::DispatchWidgetEvent(aEvent);
+}
+
+void BrowserChild::MaybeDispatchCoalescedWheelEvent() {
+  if (mCoalescedWheelData.IsEmpty()) {
+    return;
+  }
+  UniquePtr<WidgetWheelEvent> wheelEvent =
+      mCoalescedWheelData.TakeCoalescedEvent();
+  MOZ_ASSERT(wheelEvent);
+  DispatchWheelEvent(*wheelEvent, mCoalescedWheelData.GetScrollableLayerGuid(),
+                     mCoalescedWheelData.GetInputBlockId());
+}
+
+void BrowserChild::DispatchWheelEvent(const WidgetWheelEvent& aEvent,
+                                      const ScrollableLayerGuid& aGuid,
+                                      const uint64_t& aInputBlockId) {
+  WidgetWheelEvent localEvent(aEvent);
+  if (aInputBlockId && aEvent.mFlags.mHandledByAPZ) {
+    nsCOMPtr<Document> document(GetTopLevelDocument());
+    UniquePtr<DisplayportSetListener> postLayerization =
+        APZCCallbackHelper::SendSetTargetAPZCNotification(
+            mPuppetWidget, document, aEvent, aGuid.mLayersId, aInputBlockId);
+    if (postLayerization && postLayerization->Register()) {
+      Unused << postLayerization.release();
+    }
+  }
+
+  localEvent.mWidget = mPuppetWidget;
+
+  // Stash the guid in InputAPZContext so that when the visual-to-layout
+  // transform is applied to the event's coordinates, we use the right transform
+  // based on the scroll frame being targeted.
+  // The other values don't really matter.
+  InputAPZContext context(aGuid, aInputBlockId, nsEventStatus_eSentinel);
+
+  DispatchWidgetEventViaAPZ(localEvent);
+
+  if (localEvent.mCanTriggerSwipe) {
+    SendRespondStartSwipeEvent(aInputBlockId, localEvent.TriggersSwipe());
+  }
+
+  if (aInputBlockId && aEvent.mFlags.mHandledByAPZ) {
+    mAPZEventState->ProcessWheelEvent(localEvent, aInputBlockId);
+  }
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvMouseWheelEvent(
+    const WidgetWheelEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  bool isNextWheelEvent = false;
+  if (MaybeCoalesceWheelEvent(aEvent, aGuid, aInputBlockId,
+                              &isNextWheelEvent)) {
+    return IPC_OK();
+  }
+  if (isNextWheelEvent) {
+    // Update mLastWheelProcessedTimeFromParent so that we can compare the end
+    // time of the current event with the dispatched time of the next event.
+    mLastWheelProcessedTimeFromParent = aEvent.mTimeStamp;
+    mozilla::TimeStamp beforeDispatchingTime = TimeStamp::Now();
+    MaybeDispatchCoalescedWheelEvent();
+    DispatchWheelEvent(aEvent, aGuid, aInputBlockId);
+    mLastWheelProcessingDuration = (TimeStamp::Now() - beforeDispatchingTime);
+    mLastWheelProcessedTimeFromParent += mLastWheelProcessingDuration;
+  } else {
+    // This is the last wheel event. Set mLastWheelProcessedTimeFromParent to
+    // null moment to avoid coalesce the next incoming wheel event.
+    mLastWheelProcessedTimeFromParent = TimeStamp();
+    MaybeDispatchCoalescedWheelEvent();
+    DispatchWheelEvent(aEvent, aGuid, aInputBlockId);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityMouseWheelEvent(
+    const WidgetWheelEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId) {
+  return RecvMouseWheelEvent(aEvent, aGuid, aInputBlockId);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealTouchEvent(
+    const WidgetTouchEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId, const nsEventStatus& aApzResponse) {
+  MOZ_LOG(sApzChildLog, LogLevel::Debug,
+          ("Receiving touch event of type %d\n", aEvent.mMessage));
+
+  WidgetTouchEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+
+  // Stash the guid in InputAPZContext so that when the visual-to-layout
+  // transform is applied to the event's coordinates, we use the right transform
+  // based on the scroll frame being targeted.
+  // The other values don't really matter.
+  InputAPZContext context(aGuid, aInputBlockId, aApzResponse);
+
+  nsTArray<TouchBehaviorFlags> allowedTouchBehaviors;
+  if (localEvent.mMessage == eTouchStart && AsyncPanZoomEnabled()) {
+    nsCOMPtr<Document> document = GetTopLevelDocument();
+    if (StaticPrefs::layout_css_touch_action_enabled()) {
+      allowedTouchBehaviors =
+          APZCCallbackHelper::SendSetAllowedTouchBehaviorNotification(
+              mPuppetWidget, document, localEvent, aInputBlockId,
+              mSetAllowedTouchBehaviorCallback);
+    }
+    UniquePtr<DisplayportSetListener> postLayerization =
+        APZCCallbackHelper::SendSetTargetAPZCNotification(
+            mPuppetWidget, document, localEvent, aGuid.mLayersId,
+            aInputBlockId);
+    if (postLayerization && postLayerization->Register()) {
+      Unused << postLayerization.release();
+    }
+  }
+
+  // Dispatch event to content (potentially a long-running operation)
+  nsEventStatus status = DispatchWidgetEventViaAPZ(localEvent);
+
+  if (!AsyncPanZoomEnabled()) {
+    // We shouldn't have any e10s platforms that have touch events enabled
+    // without APZ.
+    MOZ_ASSERT(false);
+    return IPC_OK();
+  }
+
+  mAPZEventState->ProcessTouchEvent(localEvent, aGuid, aInputBlockId,
+                                    aApzResponse, status,
+                                    std::move(allowedTouchBehaviors));
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealTouchEvent(
+    const WidgetTouchEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId, const nsEventStatus& aApzResponse) {
+  return RecvRealTouchEvent(aEvent, aGuid, aInputBlockId, aApzResponse);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealTouchMoveEvent(
+    const WidgetTouchEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId, const nsEventStatus& aApzResponse) {
+  if (!RecvRealTouchEvent(aEvent, aGuid, aInputBlockId, aApzResponse)) {
+    return IPC_FAIL_NO_REASON(this);
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealTouchMoveEvent(
+    const WidgetTouchEvent& aEvent, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId, const nsEventStatus& aApzResponse) {
+  return RecvRealTouchMoveEvent(aEvent, aGuid, aInputBlockId, aApzResponse);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealDragEvent(
+    const WidgetDragEvent& aEvent, const uint32_t& aDragAction,
+    const uint32_t& aDropEffect, nsIPrincipal* aPrincipal,
+    nsIContentSecurityPolicy* aCsp) {
+  WidgetDragEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+
+  nsCOMPtr<nsIDragSession> dragSession = nsContentUtils::GetDragSession();
+  if (dragSession) {
+    dragSession->SetDragAction(aDragAction);
+    dragSession->SetTriggeringPrincipal(aPrincipal);
+    dragSession->SetCsp(aCsp);
+    RefPtr<DataTransfer> initialDataTransfer = dragSession->GetDataTransfer();
+    if (initialDataTransfer) {
+      initialDataTransfer->SetDropEffectInt(aDropEffect);
+    }
+  }
+
+  if (aEvent.mMessage == eDrop) {
+    bool canDrop = true;
+    if (!dragSession || NS_FAILED(dragSession->GetCanDrop(&canDrop)) ||
+        !canDrop) {
+      localEvent.mMessage = eDragExit;
+    }
+  } else if (aEvent.mMessage == eDragOver) {
+    nsCOMPtr<nsIDragService> dragService =
+        do_GetService("@mozilla.org/widget/dragservice;1");
+    if (dragService) {
+      // This will dispatch 'drag' event at the source if the
+      // drag transaction started in this process.
+      dragService->FireDragEventAtSource(eDrag, aEvent.mModifiers);
+    }
+  }
+
+  DispatchWidgetEventViaAPZ(localEvent);
+  return IPC_OK();
+}
+
+void BrowserChild::RequestEditCommands(nsIWidget::NativeKeyBindingsType aType,
+                                       const WidgetKeyboardEvent& aEvent,
+                                       nsTArray<CommandInt>& aCommands) {
+  MOZ_ASSERT(aCommands.IsEmpty());
+
+  if (NS_WARN_IF(aEvent.IsEditCommandsInitialized(aType))) {
+    aCommands = aEvent.EditCommandsConstRef(aType).Clone();
+    return;
+  }
+
+  switch (aType) {
+    case nsIWidget::NativeKeyBindingsForSingleLineEditor:
+    case nsIWidget::NativeKeyBindingsForMultiLineEditor:
+    case nsIWidget::NativeKeyBindingsForRichTextEditor:
+      break;
+    default:
+      MOZ_ASSERT_UNREACHABLE("Invalid native key bindings type");
+  }
+
+  // Don't send aEvent to the parent process directly because it'll be marked
+  // as posted to remote process.
+  WidgetKeyboardEvent localEvent(aEvent);
+  SendRequestNativeKeyBindings(aType, localEvent, &aCommands);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNativeSynthesisResponse(
+    const uint64_t& aObserverId, const nsCString& aResponse) {
+  mozilla::widget::AutoObserverNotifier::NotifySavedObserver(aObserverId,
+                                                             aResponse.get());
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvFlushTabState(
+    const uint32_t& aFlushId, const bool& aIsFinal) {
+  UpdateSessionStore(aFlushId, aIsFinal);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvUpdateEpoch(const uint32_t& aEpoch) {
+  mSessionStoreListener->SetEpoch(aEpoch);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvUpdateSHistory(
+    const bool& aImmediately) {
+  if (mSessionStoreListener) {
+    mSessionStoreListener->UpdateSHistoryChanges(aImmediately);
+  }
+  return IPC_OK();
+}
+
+// In case handling repeated keys takes much time, we skip firing new ones.
+bool BrowserChild::SkipRepeatedKeyEvent(const WidgetKeyboardEvent& aEvent) {
+  if (mRepeatedKeyEventTime.IsNull() || !aEvent.CanSkipInRemoteProcess() ||
+      (aEvent.mMessage != eKeyDown && aEvent.mMessage != eKeyPress)) {
+    mRepeatedKeyEventTime = TimeStamp();
+    mSkipKeyPress = false;
+    return false;
+  }
+
+  if ((aEvent.mMessage == eKeyDown &&
+       (mRepeatedKeyEventTime > aEvent.mTimeStamp)) ||
+      (mSkipKeyPress && (aEvent.mMessage == eKeyPress))) {
+    // If we skip a keydown event, also the following keypress events should be
+    // skipped.
+    mSkipKeyPress |= aEvent.mMessage == eKeyDown;
+    return true;
+  }
+
+  if (aEvent.mMessage == eKeyDown) {
+    // If keydown wasn't skipped, nor should the possible following keypress.
+    mRepeatedKeyEventTime = TimeStamp();
+    mSkipKeyPress = false;
+  }
+  return false;
+}
+
+void BrowserChild::UpdateRepeatedKeyEventEndTime(
+    const WidgetKeyboardEvent& aEvent) {
+  if (aEvent.mIsRepeat &&
+      (aEvent.mMessage == eKeyDown || aEvent.mMessage == eKeyPress)) {
+    mRepeatedKeyEventTime = TimeStamp::Now();
+  }
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRealKeyEvent(
+    const WidgetKeyboardEvent& aEvent) {
+  if (SkipRepeatedKeyEvent(aEvent)) {
+    return IPC_OK();
+  }
+
+  MOZ_ASSERT(
+      aEvent.mMessage != eKeyPress || aEvent.AreAllEditCommandsInitialized(),
+      "eKeyPress event should have native key binding information");
+
+  // If content code called preventDefault() on a keydown event, then we don't
+  // want to process any following keypress events.
+  if (aEvent.mMessage == eKeyPress && mIgnoreKeyPressEvent) {
+    return IPC_OK();
+  }
+
+  WidgetKeyboardEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+  localEvent.mUniqueId = aEvent.mUniqueId;
+  nsEventStatus status = DispatchWidgetEventViaAPZ(localEvent);
+
+  // Update the end time of the possible repeated event so that we can skip
+  // some incoming events in case event handling took long time.
+  UpdateRepeatedKeyEventEndTime(localEvent);
+
+  if (aEvent.mMessage == eKeyDown) {
+    mIgnoreKeyPressEvent = status == nsEventStatus_eConsumeNoDefault;
+  }
+
+  if (localEvent.mFlags.mIsSuppressedOrDelayed) {
+    localEvent.PreventDefault();
+  }
+
+  // If a response is desired from the content process, resend the key event.
+  if (aEvent.WantReplyFromContentProcess()) {
+    // If the event's default isn't prevented but the status is no default,
+    // That means that the event was consumed by EventStateManager or something
+    // which is not a usual event handler.  In such case, prevent its default
+    // as a default handler.  For example, when an eKeyPress event matches
+    // with a content accesskey, and it's executed, peventDefault() of the
+    // event won't be called but the status is set to "no default".  Then,
+    // the event shouldn't be handled by nsMenuBarListener in the main process.
+    if (!localEvent.DefaultPrevented() &&
+        status == nsEventStatus_eConsumeNoDefault) {
+      localEvent.PreventDefault();
+    }
+    // This is an ugly hack, mNoRemoteProcessDispatch is set to true when the
+    // event's PreventDefault() or StopScrollProcessForwarding() is called.
+    // And then, it'll be checked by ParamTraits<mozilla::WidgetEvent>::Write()
+    // whether the event is being sent to remote process unexpectedly.
+    // However, unfortunately, it cannot check the destination.  Therefore,
+    // we need to clear the flag explicitly here because ParamTraits should
+    // keep checking the flag for avoiding regression.
+    localEvent.mFlags.mNoRemoteProcessDispatch = false;
+    SendReplyKeyEvent(localEvent);
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityRealKeyEvent(
+    const WidgetKeyboardEvent& aEvent) {
+  return RecvRealKeyEvent(aEvent);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvCompositionEvent(
+    const WidgetCompositionEvent& aEvent) {
+  WidgetCompositionEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+  DispatchWidgetEventViaAPZ(localEvent);
+  Unused << SendOnEventNeedingAckHandled(aEvent.mMessage);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPriorityCompositionEvent(
+    const WidgetCompositionEvent& aEvent) {
+  return RecvCompositionEvent(aEvent);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSelectionEvent(
+    const WidgetSelectionEvent& aEvent) {
+  WidgetSelectionEvent localEvent(aEvent);
+  localEvent.mWidget = mPuppetWidget;
+  DispatchWidgetEventViaAPZ(localEvent);
+  Unused << SendOnEventNeedingAckHandled(aEvent.mMessage);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNormalPrioritySelectionEvent(
+    const WidgetSelectionEvent& aEvent) {
+  return RecvSelectionEvent(aEvent);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvPasteTransferable(
+    const IPCDataTransfer& aDataTransfer, const bool& aIsPrivateData,
+    nsIPrincipal* aRequestingPrincipal,
+    const nsContentPolicyType& aContentPolicyType) {
+  nsresult rv;
+  nsCOMPtr<nsITransferable> trans =
+      do_CreateInstance("@mozilla.org/widget/transferable;1", &rv);
+  NS_ENSURE_SUCCESS(rv, IPC_OK());
+  trans->Init(nullptr);
+
+  rv = nsContentUtils::IPCTransferableToTransferable(
+      aDataTransfer, aIsPrivateData, aRequestingPrincipal, aContentPolicyType,
+      trans, nullptr, this);
+  NS_ENSURE_SUCCESS(rv, IPC_OK());
+
+  nsCOMPtr<nsIDocShell> ourDocShell = do_GetInterface(WebNavigation());
+  if (NS_WARN_IF(!ourDocShell)) {
+    return IPC_OK();
+  }
+
+  RefPtr<nsCommandParams> params = new nsCommandParams();
+  rv = params->SetISupports("transferable", trans);
+  NS_ENSURE_SUCCESS(rv, IPC_OK());
+
+  ourDocShell->DoCommandWithParams("cmd_pasteTransferable", params);
+  return IPC_OK();
+}
+
+#ifdef ACCESSIBILITY
+a11y::PDocAccessibleChild* BrowserChild::AllocPDocAccessibleChild(
+    PDocAccessibleChild*, const uint64_t&, const uint32_t&,
+    const IAccessibleHolder&) {
+  MOZ_ASSERT(false, "should never call this!");
+  return nullptr;
+}
+
+bool BrowserChild::DeallocPDocAccessibleChild(
+    a11y::PDocAccessibleChild* aChild) {
+  delete static_cast<mozilla::a11y::DocAccessibleChild*>(aChild);
+  return true;
+}
+#endif
+
+PColorPickerChild* BrowserChild::AllocPColorPickerChild(const nsString&,
+                                                        const nsString&) {
+  MOZ_CRASH("unused");
+  return nullptr;
+}
+
+bool BrowserChild::DeallocPColorPickerChild(PColorPickerChild* aColorPicker) {
+  nsColorPickerProxy* picker = static_cast<nsColorPickerProxy*>(aColorPicker);
+  NS_RELEASE(picker);
+  return true;
+}
+
+PFilePickerChild* BrowserChild::AllocPFilePickerChild(const nsString&,
+                                                      const int16_t&) {
+  MOZ_CRASH("unused");
+  return nullptr;
+}
+
+bool BrowserChild::DeallocPFilePickerChild(PFilePickerChild* actor) {
+  nsFilePickerProxy* filePicker = static_cast<nsFilePickerProxy*>(actor);
+  NS_RELEASE(filePicker);
+  return true;
+}
+
+PVsyncChild* BrowserChild::AllocPVsyncChild() {
+  RefPtr<dom::VsyncChild> actor = new VsyncChild();
+  // There still has one ref-count after return, and it will be released in
+  // DeallocPVsyncChild().
+  return actor.forget().take();
+}
+
+bool BrowserChild::DeallocPVsyncChild(PVsyncChild* aActor) {
+  MOZ_ASSERT(aActor);
+
+  // This actor already has one ref-count. Please check AllocPVsyncChild().
+  RefPtr<VsyncChild> actor = dont_AddRef(static_cast<VsyncChild*>(aActor));
+  return true;
+}
+
+RefPtr<VsyncChild> BrowserChild::GetVsyncChild() {
+  // Initializing mVsyncChild here turns on per-BrowserChild Vsync for a
+  // given platform. Note: this only makes sense if nsWindow returns a
+  // window-specific VsyncSource.
+#if defined(MOZ_WAYLAND)
+  if (!IsWaylandDisabled() && !mVsyncChild) {
+    PVsyncChild* actor = SendPVsyncConstructor();
+    mVsyncChild = static_cast<VsyncChild*>(actor);
+  }
+#endif
+  return mVsyncChild;
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvActivateFrameEvent(
+    const nsString& aType, const bool& capture) {
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+  NS_ENSURE_TRUE(window, IPC_OK());
+  nsCOMPtr<EventTarget> chromeHandler = window->GetChromeEventHandler();
+  NS_ENSURE_TRUE(chromeHandler, IPC_OK());
+  RefPtr<ContentListener> listener = new ContentListener(this);
+  chromeHandler->AddEventListener(aType, listener, capture);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvLoadRemoteScript(
+    const nsString& aURL, const bool& aRunInGlobalScope) {
+  if (!InitBrowserChildMessageManager())
+    // This can happen if we're half-destroyed.  It's not a fatal
+    // error.
+    return IPC_OK();
+
+  JS::Rooted<JSObject*> mm(RootingCx(),
+                           mBrowserChildMessageManager->GetOrCreateWrapper());
+  if (!mm) {
+    // This can happen if we're half-destroyed.  It's not a fatal error.
+    return IPC_OK();
+  }
+
+  LoadScriptInternal(mm, aURL, !aRunInGlobalScope);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvAsyncMessage(
+    const nsString& aMessage, const ClonedMessageData& aData) {
+  AUTO_PROFILER_LABEL_DYNAMIC_LOSSY_NSSTRING("BrowserChild::RecvAsyncMessage",
+                                             OTHER, aMessage);
+  MMPrinter::Print("BrowserChild::RecvAsyncMessage", aMessage, aData);
+
+  if (!mBrowserChildMessageManager) {
+    return IPC_OK();
+  }
+
+  RefPtr<nsFrameMessageManager> mm =
+      mBrowserChildMessageManager->GetMessageManager();
+
+  // We should have a message manager if the global is alive, but it
+  // seems sometimes we don't.  Assert in aurora/nightly, but don't
+  // crash in release builds.
+  MOZ_DIAGNOSTIC_ASSERT(mm);
+  if (!mm) {
+    return IPC_OK();
+  }
+
+  JS::Rooted<JSObject*> kungFuDeathGrip(
+      dom::RootingCx(), mBrowserChildMessageManager->GetWrapper());
+  StructuredCloneData data;
+  UnpackClonedMessageDataForChild(aData, data);
+  mm->ReceiveMessage(static_cast<EventTarget*>(mBrowserChildMessageManager),
+                     nullptr, aMessage, false, &data, nullptr, IgnoreErrors());
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSwappedWithOtherRemoteLoader(
+    const IPCTabContext& aContext) {
+  nsCOMPtr<nsIDocShell> ourDocShell = do_GetInterface(WebNavigation());
+  if (NS_WARN_IF(!ourDocShell)) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> ourWindow = ourDocShell->GetWindow();
+  if (NS_WARN_IF(!ourWindow)) {
+    return IPC_OK();
+  }
+
+  RefPtr<nsDocShell> docShell = static_cast<nsDocShell*>(ourDocShell.get());
+
+  nsCOMPtr<EventTarget> ourEventTarget = nsGlobalWindowOuter::Cast(ourWindow);
+
+  docShell->SetInFrameSwap(true);
+
+  nsContentUtils::FirePageShowEventForFrameLoaderSwap(
+      ourDocShell, ourEventTarget, false, true);
+  nsContentUtils::FirePageHideEventForFrameLoaderSwap(ourDocShell,
+                                                      ourEventTarget, true);
+
+  // Owner content type may have changed, so store the possibly updated context
+  // and notify others.
+  MaybeInvalidTabContext maybeContext(aContext);
+  if (!maybeContext.IsValid()) {
+    NS_ERROR(nsPrintfCString("Received an invalid TabContext from "
+                             "the parent process. (%s)",
+                             maybeContext.GetInvalidReason())
+                 .get());
+    MOZ_CRASH("Invalid TabContext received from the parent process.");
+  }
+
+  if (!UpdateTabContextAfterSwap(maybeContext.GetTabContext())) {
+    MOZ_CRASH("Update to TabContext after swap was denied.");
+  }
+
+  // Ignore previous value of mTriedBrowserInit since owner content has changed.
+  mTriedBrowserInit = true;
+
+  nsContentUtils::FirePageShowEventForFrameLoaderSwap(
+      ourDocShell, ourEventTarget, true, true);
+
+  docShell->SetInFrameSwap(false);
+
+  // This is needed to get visibility state right in cases when we swapped a
+  // visible tab (foreground in visible window) with a non-visible tab.
+  if (RefPtr<Document> doc = docShell->GetDocument()) {
+    doc->UpdateVisibilityState();
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvHandleAccessKey(
+    const WidgetKeyboardEvent& aEvent, nsTArray<uint32_t>&& aCharCodes) {
+  nsCOMPtr<Document> document(GetTopLevelDocument());
+  RefPtr<nsPresContext> pc = document->GetPresContext();
+  if (pc) {
+    if (!pc->EventStateManager()->HandleAccessKey(
+            &(const_cast<WidgetKeyboardEvent&>(aEvent)), pc, aCharCodes)) {
+      // If no accesskey was found, inform the parent so that accesskeys on
+      // menus can be handled.
+      WidgetKeyboardEvent localEvent(aEvent);
+      localEvent.mWidget = mPuppetWidget;
+      SendAccessKeyNotHandled(localEvent);
+    }
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvPrintPreview(
+    const PrintData& aPrintData,
+    const mozilla::Maybe<uint64_t>& aSourceOuterWindowID,
+    PrintPreviewResolver&& aCallback) {
+#ifdef NS_PRINTING
+  // If we didn't succeed in passing off ownership of aCallback, then something
+  // went wrong.
+  auto sendCallbackError = MakeScopeExit([&] {
+    if (aCallback) {
+      aCallback(
+          PrintPreviewResultInfo(0, 0, false, false, false));  // signal error
+    }
+  });
+
+  RefPtr<nsGlobalWindowOuter> sourceWindow;
+  if (aSourceOuterWindowID) {
+    sourceWindow =
+        nsGlobalWindowOuter::GetOuterWindowWithId(aSourceOuterWindowID.value());
+    if (NS_WARN_IF(!sourceWindow)) {
+      return IPC_OK();
+    }
+  } else {
+    nsCOMPtr<nsPIDOMWindowOuter> ourWindow = do_GetInterface(WebNavigation());
+    if (NS_WARN_IF(!ourWindow)) {
+      return IPC_OK();
+    }
+    sourceWindow = nsGlobalWindowOuter::Cast(ourWindow);
+  }
+
+  RefPtr<nsIPrintSettings> printSettings;
+  nsCOMPtr<nsIPrintSettingsService> printSettingsSvc =
+      do_GetService("@mozilla.org/gfx/printsettings-service;1");
+  if (NS_WARN_IF(!printSettingsSvc)) {
+    return IPC_OK();
+  }
+  printSettingsSvc->GetNewPrintSettings(getter_AddRefs(printSettings));
+  if (NS_WARN_IF(!printSettings)) {
+    return IPC_OK();
+  }
+  printSettingsSvc->DeserializeToPrintSettings(aPrintData, printSettings);
+
+  nsCOMPtr<nsIDocShell> docShellToCloneInto;
+  if (aSourceOuterWindowID) {
+    docShellToCloneInto = do_GetInterface(WebNavigation());
+    if (NS_WARN_IF(!docShellToCloneInto)) {
+      return IPC_OK();
+    }
+  }
+
+  sourceWindow->Print(printSettings,
+                      /* aListener = */ nullptr, docShellToCloneInto,
+                      nsGlobalWindowOuter::IsPreview::Yes,
+                      nsGlobalWindowOuter::IsForWindowDotPrint::No,
+                      std::move(aCallback), IgnoreErrors());
+#endif
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvExitPrintPreview() {
+#ifdef NS_PRINTING
+  nsCOMPtr<nsIWebBrowserPrint> webBrowserPrint =
+      do_GetInterface(ToSupports(WebNavigation()));
+  if (NS_WARN_IF(!webBrowserPrint)) {
+    return IPC_OK();
+  }
+  webBrowserPrint->ExitPrintPreview();
+#endif
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvPrint(const uint64_t& aOuterWindowID,
+                                                const PrintData& aPrintData) {
+#ifdef NS_PRINTING
+  RefPtr<nsGlobalWindowOuter> outerWindow =
+      nsGlobalWindowOuter::GetOuterWindowWithId(aOuterWindowID);
+  if (NS_WARN_IF(!outerWindow)) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIPrintSettingsService> printSettingsSvc =
+      do_GetService("@mozilla.org/gfx/printsettings-service;1");
+  if (NS_WARN_IF(!printSettingsSvc)) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIPrintSettings> printSettings;
+  nsresult rv =
+      printSettingsSvc->GetNewPrintSettings(getter_AddRefs(printSettings));
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIPrintSession> printSession =
+      do_CreateInstance("@mozilla.org/gfx/printsession;1", &rv);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    return IPC_OK();
+  }
+
+  printSettings->SetPrintSession(printSession);
+  printSettingsSvc->DeserializeToPrintSettings(aPrintData, printSettings);
+  {
+    IgnoredErrorResult rv;
+    outerWindow->Print(printSettings,
+                       /* aListener = */ nullptr,
+                       /* aWindowToCloneInto = */ nullptr,
+                       nsGlobalWindowOuter::IsPreview::No,
+                       nsGlobalWindowOuter::IsForWindowDotPrint::No,
+                       /* aPrintPreviewCallback = */ nullptr, rv);
+    if (NS_WARN_IF(rv.Failed())) {
+      return IPC_OK();
+    }
+  }
+#endif
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvUpdateNativeWindowHandle(
+    const uintptr_t& aNewHandle) {
+#if defined(XP_WIN) && defined(ACCESSIBILITY)
+  mNativeWindowHandle = aNewHandle;
+  return IPC_OK();
+#else
+  return IPC_FAIL_NO_REASON(this);
+#endif
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvDestroy() {
+  MOZ_ASSERT(mDestroyed == false);
+  mDestroyed = true;
+
+  nsTArray<PContentPermissionRequestChild*> childArray =
+      nsContentPermissionUtils::GetContentPermissionRequestChildById(
+          GetTabId());
+
+  // Need to close undeleted ContentPermissionRequestChilds before tab is
+  // closed.
+  for (auto& permissionRequestChild : childArray) {
+    auto child = static_cast<RemotePermissionRequest*>(permissionRequestChild);
+    child->Destroy();
+  }
+
+  if (mBrowserChildMessageManager) {
+    // Message handlers are called from the event loop, so it better be safe to
+    // run script.
+    MOZ_ASSERT(nsContentUtils::IsSafeToRunScript());
+    mBrowserChildMessageManager->DispatchTrustedEvent(u"unload"_ns);
+  }
+
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+
+  observerService->RemoveObserver(this, BEFORE_FIRST_PAINT);
+
+  // XXX what other code in ~BrowserChild() should we be running here?
+  DestroyWindow();
+
+  // Bounce through the event loop once to allow any delayed teardown runnables
+  // that were just generated to have a chance to run.
+  nsCOMPtr<nsIRunnable> deleteRunnable = new DelayedDeleteRunnable(this);
+  MOZ_ALWAYS_SUCCEEDS(NS_DispatchToCurrentThread(deleteRunnable));
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRenderLayers(
+    const bool& aEnabled, const layers::LayersObserverEpoch& aEpoch) {
+  if (mPendingDocShellBlockers > 0) {
+    mPendingRenderLayersReceivedMessage = true;
+    mPendingRenderLayers = aEnabled;
+    mPendingLayersObserverEpoch = aEpoch;
+    return IPC_OK();
+  }
+
+  // Since requests to change the rendering state come in from both the hang
+  // monitor channel and the PContent channel, we have an ordering problem. This
+  // code ensures that we respect the order in which the requests were made and
+  // ignore stale requests.
+  if (mLayersObserverEpoch >= aEpoch) {
+    return IPC_OK();
+  }
+  mLayersObserverEpoch = aEpoch;
+
+  auto clearPaintWhileInterruptingJS = MakeScopeExit([&] {
+    // We might force a paint, or we might already have painted and this is a
+    // no-op. In either case, once we exit this scope, we need to alert the
+    // ProcessHangMonitor that we've finished responding to what might have
+    // been a request to force paint. This is so that the BackgroundHangMonitor
+    // for force painting can be made to wait again.
+    if (aEnabled) {
+      ProcessHangMonitor::ClearPaintWhileInterruptingJS(mLayersObserverEpoch);
+    }
+  });
+
+  if (aEnabled) {
+    ProcessHangMonitor::MaybeStartPaintWhileInterruptingJS();
+  }
+
+  if (mCompositorOptions) {
+    MOZ_ASSERT(mPuppetWidget);
+    RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+    MOZ_ASSERT(lm);
+
+    // We send the current layer observer epoch to the compositor so that
+    // BrowserParent knows whether a layer update notification corresponds to
+    // the latest RecvRenderLayers request that was made.
+    lm->SetLayersObserverEpoch(mLayersObserverEpoch);
+  }
+
+  mRenderLayers = aEnabled;
+
+  if (aEnabled && IsVisible()) {
+    // This request is a no-op.
+    // In this case, we still want a MozLayerTreeReady notification to fire
+    // in the parent (so that it knows that the child has updated its epoch).
+    // PaintWhileInterruptingJSNoOp does that.
+    if (IPCOpen()) {
+      Unused << SendPaintWhileInterruptingJSNoOp(mLayersObserverEpoch);
+    }
+    return IPC_OK();
+  }
+
+  // FIXME(emilio): Probably / maybe this shouldn't be needed? See the comment
+  // in MakeVisible(), having the two separate states is not great.
+  UpdateVisibility();
+
+  if (!aEnabled) {
+    return IPC_OK();
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  if (!docShell) {
+    return IPC_OK();
+  }
+
+  // We don't use BrowserChildBase::GetPresShell() here because that would
+  // create a content viewer if one doesn't exist yet. Creating a content
+  // viewer can cause JS to run, which we want to avoid.
+  // nsIDocShell::GetPresShell returns null if no content viewer exists yet.
+  RefPtr<PresShell> presShell = docShell->GetPresShell();
+  if (!presShell) {
+    return IPC_OK();
+  }
+
+  if (nsIFrame* root = presShell->GetRootFrame()) {
+    FrameLayerBuilder::InvalidateAllLayersForFrame(
+        nsLayoutUtils::GetDisplayRootFrame(root));
+    root->SchedulePaint();
+  }
+
+  Telemetry::AutoTimer<Telemetry::TABCHILD_PAINT_TIME> timer;
+  // If we need to repaint, let's do that right away. No sense waiting until
+  // we get back to the event loop again. We suppress the display port so
+  // that we only paint what's visible. This ensures that the tab we're
+  // switching to paints as quickly as possible.
+  presShell->SuppressDisplayport(true);
+  if (nsContentUtils::IsSafeToRunScript()) {
+    WebWidget()->PaintNowIfNeeded();
+  } else {
+    RefPtr<nsViewManager> vm = presShell->GetViewManager();
+    if (nsView* view = vm->GetRootView()) {
+      presShell->Paint(view, view->GetBounds(), PaintFlags::PaintLayers);
+    }
+  }
+  presShell->SuppressDisplayport(false);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvNavigateByKey(
+    const bool& aForward, const bool& aForDocumentNavigation) {
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  if (!fm) {
+    return IPC_OK();
+  }
+
+  RefPtr<Element> result;
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+
+  // Move to the first or last document.
+  {
+    uint32_t type =
+        aForward
+            ? (aForDocumentNavigation
+                   ? static_cast<uint32_t>(nsIFocusManager::MOVEFOCUS_FIRSTDOC)
+                   : static_cast<uint32_t>(nsIFocusManager::MOVEFOCUS_ROOT))
+            : (aForDocumentNavigation
+                   ? static_cast<uint32_t>(nsIFocusManager::MOVEFOCUS_LASTDOC)
+                   : static_cast<uint32_t>(nsIFocusManager::MOVEFOCUS_LAST));
+    uint32_t flags = nsIFocusManager::FLAG_BYKEY;
+    if (aForward || aForDocumentNavigation) {
+      flags |= nsIFocusManager::FLAG_NOSCROLL;
+    }
+    fm->MoveFocus(window, nullptr, type, flags, getter_AddRefs(result));
+  }
+
+  // No valid root element was found, so move to the first focusable element.
+  if (!result && aForward && !aForDocumentNavigation) {
+    fm->MoveFocus(window, nullptr, nsIFocusManager::MOVEFOCUS_FIRST,
+                  nsIFocusManager::FLAG_BYKEY, getter_AddRefs(result));
+  }
+
+  SendRequestFocus(false, CallerType::System);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvHandledWindowedPluginKeyEvent(
+    const NativeEventData& aKeyEventData, const bool& aIsConsumed) {
+  if (NS_WARN_IF(!mPuppetWidget)) {
+    return IPC_OK();
+  }
+  mPuppetWidget->HandledWindowedPluginKeyEvent(aKeyEventData, aIsConsumed);
+  return IPC_OK();
+}
+
+bool BrowserChild::InitBrowserChildMessageManager() {
+  if (!mBrowserChildMessageManager) {
+    nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+    NS_ENSURE_TRUE(window, false);
+    nsCOMPtr<EventTarget> chromeHandler = window->GetChromeEventHandler();
+    NS_ENSURE_TRUE(chromeHandler, false);
+
+    RefPtr<BrowserChildMessageManager> scope = mBrowserChildMessageManager =
+        new BrowserChildMessageManager(this);
+
+    MOZ_ALWAYS_TRUE(nsMessageManagerScriptExecutor::Init());
+
+    nsCOMPtr<nsPIWindowRoot> root = do_QueryInterface(chromeHandler);
+    if (NS_WARN_IF(!root)) {
+      mBrowserChildMessageManager = nullptr;
+      return false;
+    }
+    root->SetParentTarget(scope);
+  }
+
+  if (!mTriedBrowserInit) {
+    mTriedBrowserInit = true;
+  }
+
+  return true;
+}
+
+void BrowserChild::InitRenderingState(
+    const TextureFactoryIdentifier& aTextureFactoryIdentifier,
+    const layers::LayersId& aLayersId,
+    const CompositorOptions& aCompositorOptions) {
+  mPuppetWidget->InitIMEState();
+
+  MOZ_ASSERT(aLayersId.IsValid());
+  mTextureFactoryIdentifier = aTextureFactoryIdentifier;
+
+  // Pushing layers transactions directly to a separate
+  // compositor context.
+  PCompositorBridgeChild* compositorChild = CompositorBridgeChild::Get();
+  if (!compositorChild) {
+    mLayersConnected = Some(false);
+    NS_WARNING("failed to get CompositorBridgeChild instance");
+    return;
+  }
+
+  mCompositorOptions = Some(aCompositorOptions);
+
+  if (aLayersId.IsValid()) {
+    StaticMutexAutoLock lock(sBrowserChildrenMutex);
+
+    if (!sBrowserChildren) {
+      sBrowserChildren = new BrowserChildMap;
+    }
+    MOZ_ASSERT(!sBrowserChildren->Get(uint64_t(aLayersId)));
+    sBrowserChildren->Put(uint64_t(aLayersId), this);
+    mLayersId = aLayersId;
+  }
+
+  // Depending on timing, we might paint too early and fall back to basic
+  // layers. CreateRemoteLayerManager will destroy us if we manage to get a
+  // remote layer manager though, so that's fine.
+  MOZ_ASSERT(!mPuppetWidget->HasLayerManager() ||
+             mPuppetWidget->GetLayerManager()->GetBackendType() ==
+                 layers::LayersBackend::LAYERS_BASIC);
+  bool success = false;
+  if (mLayersConnected == Some(true)) {
+    success = CreateRemoteLayerManager(compositorChild);
+  }
+
+  if (success) {
+    MOZ_ASSERT(mLayersConnected == Some(true));
+    // Succeeded to create "remote" layer manager
+    ImageBridgeChild::IdentifyCompositorTextureHost(mTextureFactoryIdentifier);
+    gfx::VRManagerChild::IdentifyTextureHost(mTextureFactoryIdentifier);
+    InitAPZState();
+    RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+    MOZ_ASSERT(lm);
+    lm->SetLayersObserverEpoch(mLayersObserverEpoch);
+  } else {
+    NS_WARNING("Fallback to BasicLayerManager");
+    mLayersConnected = Some(false);
+  }
+
+  nsCOMPtr<nsIObserverService> observerService =
+      mozilla::services::GetObserverService();
+
+  if (observerService) {
+    observerService->AddObserver(this, BEFORE_FIRST_PAINT, false);
+  }
+}
+
+bool BrowserChild::CreateRemoteLayerManager(
+    mozilla::layers::PCompositorBridgeChild* aCompositorChild) {
+  MOZ_ASSERT(aCompositorChild);
+
+  bool success = false;
+  if (mCompositorOptions->UseWebRender()) {
+    success = mPuppetWidget->CreateRemoteLayerManager(
+        [&](LayerManager* aLayerManager) -> bool {
+          MOZ_ASSERT(aLayerManager->AsWebRenderLayerManager());
+          nsCString error;
+          return aLayerManager->AsWebRenderLayerManager()->Initialize(
+              aCompositorChild, wr::AsPipelineId(mLayersId),
+              &mTextureFactoryIdentifier, error);
+        });
+  } else {
+    nsTArray<LayersBackend> ignored;
+    PLayerTransactionChild* shadowManager =
+        aCompositorChild->SendPLayerTransactionConstructor(ignored,
+                                                           GetLayersId());
+    if (shadowManager &&
+        shadowManager->SendGetTextureFactoryIdentifier(
+            &mTextureFactoryIdentifier) &&
+        mTextureFactoryIdentifier.mParentBackend !=
+            LayersBackend::LAYERS_NONE) {
+      success = true;
+    }
+    if (!success) {
+      // Since no LayerManager is associated with the tab's widget, we will
+      // never have an opportunity to destroy the PLayerTransaction on the next
+      // device or compositor reset. Therefore, we make sure to forcefully close
+      // it here. Failure to do so will cause the next layer tree to fail to
+      // attach due since the compositor requires the old layer tree to be
+      // disassociated.
+      if (shadowManager) {
+        static_cast<LayerTransactionChild*>(shadowManager)->Destroy();
+        shadowManager = nullptr;
+      }
+      NS_WARNING("failed to allocate layer transaction");
+    } else {
+      success = mPuppetWidget->CreateRemoteLayerManager(
+          [&](LayerManager* aLayerManager) -> bool {
+            ShadowLayerForwarder* lf = aLayerManager->AsShadowForwarder();
+            lf->SetShadowManager(shadowManager);
+            lf->IdentifyTextureHost(mTextureFactoryIdentifier);
+            return true;
+          });
+    }
+  }
+  return success;
+}
+
+void BrowserChild::InitAPZState() {
+  if (!mCompositorOptions->UseAPZ()) {
+    return;
+  }
+  auto cbc = CompositorBridgeChild::Get();
+
+  // Initialize the ApzcTreeManager. This takes multiple casts because of ugly
+  // multiple inheritance.
+  PAPZCTreeManagerChild* baseProtocol =
+      cbc->SendPAPZCTreeManagerConstructor(mLayersId);
+  APZCTreeManagerChild* derivedProtocol =
+      static_cast<APZCTreeManagerChild*>(baseProtocol);
+
+  mApzcTreeManager = RefPtr<IAPZCTreeManager>(derivedProtocol);
+
+  // Initialize the GeckoContentController for this tab. We don't hold a
+  // reference because we don't need it. The ContentProcessController will hold
+  // a reference to the tab, and will be destroyed by the compositor or ipdl
+  // during destruction.
+  RefPtr<GeckoContentController> contentController =
+      new ContentProcessController(this);
+  APZChild* apzChild = new APZChild(contentController);
+  cbc->SendPAPZConstructor(apzChild, mLayersId);
+}
+
+IPCResult BrowserChild::RecvUpdateEffects(const EffectsInfo& aEffects) {
+  bool needInvalidate = false;
+  if (mEffectsInfo.IsVisible() && aEffects.IsVisible() &&
+      mEffectsInfo != aEffects) {
+    // if we are staying visible and either the visrect or scale changed we need
+    // to invalidate
+    needInvalidate = true;
+  }
+
+  mEffectsInfo = aEffects;
+  UpdateVisibility();
+
+  if (needInvalidate) {
+    nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+    if (docShell) {
+      // We don't use BrowserChildBase::GetPresShell() here because that would
+      // create a content viewer if one doesn't exist yet. Creating a content
+      // viewer can cause JS to run, which we want to avoid.
+      // nsIDocShell::GetPresShell returns null if no content viewer exists yet.
+      RefPtr<PresShell> presShell = docShell->GetPresShell();
+      if (presShell) {
+        if (nsIFrame* root = presShell->GetRootFrame()) {
+          root->InvalidateFrame();
+        }
+      }
+    }
+  }
+
+  return IPC_OK();
+}
+
+bool BrowserChild::IsVisible() {
+  return mPuppetWidget && mPuppetWidget->IsVisible();
+}
+
+void BrowserChild::UpdateVisibility() {
+  bool shouldBeVisible = mIsTopLevel ? mRenderLayers : mEffectsInfo.IsVisible();
+  bool isVisible = IsVisible();
+
+  if (shouldBeVisible != isVisible) {
+    if (shouldBeVisible) {
+      MakeVisible();
+    } else {
+      MakeHidden();
+    }
+  }
+}
+
+void BrowserChild::MakeVisible() {
+  if (IsVisible()) {
+    return;
+  }
+
+  if (mPuppetWidget) {
+    mPuppetWidget->Show(true);
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  if (!docShell) {
+    return;
+  }
+
+  // The browser / tab-switcher is responsible of fixing the browsingContext
+  // state up explicitly via SetDocShellIsActive, which propagates to children
+  // automatically.
+  //
+  // We need it not to be observable, as this used via RecvRenderLayers and co.,
+  // for stuff like async tab warming.
+  //
+  // We don't want to go through the docshell because we don't want to change
+  // the visibility state of the document, which has side effects like firing
+  // events to content, unblocking media playback, unthrottling timeouts...
+  if (RefPtr<PresShell> presShell = docShell->GetPresShell()) {
+    presShell->SetIsActive(true);
+  }
+}
+
+void BrowserChild::MakeHidden() {
+  if (!IsVisible()) {
+    return;
+  }
+
+  // Due to the nested event loop in ContentChild::ProvideWindowCommon,
+  // it's possible to be told to become hidden before we're finished
+  // setting up a layer manager. We should skip clearing cached layers
+  // in that case, since doing so might accidentally put is into
+  // BasicLayers mode.
+  if (mPuppetWidget && mPuppetWidget->HasLayerManager()) {
+    ClearCachedResources();
+  }
+
+  if (nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation())) {
+    // Hide all plugins in this tab. We don't use
+    // BrowserChildBase::GetPresShell() here because that would create a content
+    // viewer if one doesn't exist yet. Creating a content viewer can cause JS
+    // to run, which we want to avoid. nsIDocShell::GetPresShell returns null if
+    // no content viewer exists yet.
+    if (RefPtr<PresShell> presShell = docShell->GetPresShell()) {
+      if (nsPresContext* presContext = presShell->GetPresContext()) {
+        nsRootPresContext* rootPresContext = presContext->GetRootPresContext();
+        nsIFrame* rootFrame = presShell->GetRootFrame();
+        rootPresContext->ComputePluginGeometryUpdates(rootFrame, nullptr,
+                                                      nullptr);
+        rootPresContext->ApplyPluginGeometryUpdates();
+      }
+      presShell->SetIsActive(false);
+    }
+  }
+
+  if (mPuppetWidget) {
+    mPuppetWidget->Show(false);
+  }
+}
+
+NS_IMETHODIMP
+BrowserChild::GetMessageManager(ContentFrameMessageManager** aResult) {
+  RefPtr<ContentFrameMessageManager> mm(mBrowserChildMessageManager);
+  mm.forget(aResult);
+  return *aResult ? NS_OK : NS_ERROR_FAILURE;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetWebBrowserChrome(nsIWebBrowserChrome3** aWebBrowserChrome) {
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  if (nsCOMPtr<nsIWebBrowserChrome3> chrome =
+          do_QueryActor("WebBrowserChrome", docShell->GetDocument())) {
+    chrome.forget(aWebBrowserChrome);
+  } else {
+    // TODO: remove fallback
+    NS_IF_ADDREF(*aWebBrowserChrome = mWebBrowserChrome);
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::SetWebBrowserChrome(nsIWebBrowserChrome3* aWebBrowserChrome) {
+  mWebBrowserChrome = aWebBrowserChrome;
+  return NS_OK;
+}
+
+void BrowserChild::SendRequestFocus(bool aCanFocus, CallerType aCallerType) {
+  nsFocusManager* fm = nsFocusManager::GetFocusManager();
+  if (!fm) {
+    return;
+  }
+
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+  if (!window) {
+    return;
+  }
+
+  BrowsingContext* focusedBC = fm->GetFocusedBrowsingContext();
+  if (focusedBC == window->GetBrowsingContext()) {
+    // BrowsingContext has the focus already, do not request again.
+    return;
+  }
+
+  PBrowserChild::SendRequestFocus(aCanFocus, aCallerType);
+}
+
+NS_IMETHODIMP
+BrowserChild::GetTabId(uint64_t* aId) {
+  *aId = GetTabId();
+  return NS_OK;
+}
+
+void BrowserChild::SetTabId(const TabId& aTabId) {
+  MOZ_ASSERT(mUniqueId == 0);
+
+  mUniqueId = aTabId;
+  NestedBrowserChildMap()[mUniqueId] = this;
+}
+
+NS_IMETHODIMP
+BrowserChild::GetChromeOuterWindowID(uint64_t* aId) {
+  *aId = ChromeOuterWindowID();
+  return NS_OK;
+}
+
+bool BrowserChild::DoSendBlockingMessage(
+    const nsAString& aMessage, StructuredCloneData& aData,
+    nsTArray<StructuredCloneData>* aRetVal) {
+  ClonedMessageData data;
+  if (!BuildClonedMessageDataForChild(Manager(), aData, data)) {
+    return false;
+  }
+  return SendSyncMessage(PromiseFlatString(aMessage), data, aRetVal);
+}
+
+nsresult BrowserChild::DoSendAsyncMessage(const nsAString& aMessage,
+                                          StructuredCloneData& aData) {
+  ClonedMessageData data;
+  if (!BuildClonedMessageDataForChild(Manager(), aData, data)) {
+    return NS_ERROR_DOM_DATA_CLONE_ERR;
+  }
+  if (!SendAsyncMessage(PromiseFlatString(aMessage), data)) {
+    return NS_ERROR_UNEXPECTED;
+  }
+  return NS_OK;
+}
+
+/* static */
+nsTArray<RefPtr<BrowserChild>> BrowserChild::GetAll() {
+  StaticMutexAutoLock lock(sBrowserChildrenMutex);
+
+  nsTArray<RefPtr<BrowserChild>> list;
+  if (!sBrowserChildren) {
+    return list;
+  }
+
+  for (auto iter = sBrowserChildren->Iter(); !iter.Done(); iter.Next()) {
+    list.AppendElement(iter.Data());
+  }
+
+  return list;
+}
+
+BrowserChild* BrowserChild::GetFrom(PresShell* aPresShell) {
+  Document* doc = aPresShell->GetDocument();
+  if (!doc) {
+    return nullptr;
+  }
+  nsCOMPtr<nsIDocShell> docShell(doc->GetDocShell());
+  return GetFrom(docShell);
+}
+
+BrowserChild* BrowserChild::GetFrom(layers::LayersId aLayersId) {
+  StaticMutexAutoLock lock(sBrowserChildrenMutex);
+  if (!sBrowserChildren) {
+    return nullptr;
+  }
+  return sBrowserChildren->Get(uint64_t(aLayersId));
+}
+
+void BrowserChild::DidComposite(mozilla::layers::TransactionId aTransactionId,
+                                const TimeStamp& aCompositeStart,
+                                const TimeStamp& aCompositeEnd) {
+  MOZ_ASSERT(mPuppetWidget);
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
+  lm->DidComposite(aTransactionId, aCompositeStart, aCompositeEnd);
+}
+
+void BrowserChild::DidRequestComposite(const TimeStamp& aCompositeReqStart,
+                                       const TimeStamp& aCompositeReqEnd) {
+  nsCOMPtr<nsIDocShell> docShellComPtr = do_GetInterface(WebNavigation());
+  if (!docShellComPtr) {
+    return;
+  }
+
+  nsDocShell* docShell = static_cast<nsDocShell*>(docShellComPtr.get());
+  RefPtr<TimelineConsumers> timelines = TimelineConsumers::Get();
+
+  if (timelines && timelines->HasConsumer(docShell)) {
+    // Since we're assuming that it's impossible for content JS to directly
+    // trigger a synchronous paint, we can avoid capturing a stack trace here,
+    // which means we won't run into JS engine reentrancy issues like bug
+    // 1310014.
+    timelines->AddMarkerForDocShell(
+        docShell, "CompositeForwardTransaction", aCompositeReqStart,
+        MarkerTracingType::START, MarkerStackRequest::NO_STACK);
+    timelines->AddMarkerForDocShell(docShell, "CompositeForwardTransaction",
+                                    aCompositeReqEnd, MarkerTracingType::END,
+                                    MarkerStackRequest::NO_STACK);
+  }
+}
+
+void BrowserChild::ClearCachedResources() {
+  MOZ_ASSERT(mPuppetWidget);
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
+  lm->ClearCachedResources();
+
+  if (nsCOMPtr<Document> document = GetTopLevelDocument()) {
+    nsPresContext* presContext = document->GetPresContext();
+    if (presContext) {
+      presContext->NotifyPaintStatusReset();
+    }
+  }
+}
+
+void BrowserChild::InvalidateLayers() {
+  MOZ_ASSERT(mPuppetWidget);
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+
+  FrameLayerBuilder::InvalidateAllLayers(lm);
+}
+
+void BrowserChild::SchedulePaint() {
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  if (!docShell) {
+    return;
+  }
+
+  // We don't use BrowserChildBase::GetPresShell() here because that would
+  // create a content viewer if one doesn't exist yet. Creating a content viewer
+  // can cause JS to run, which we want to avoid. nsIDocShell::GetPresShell
+  // returns null if no content viewer exists yet.
+  if (RefPtr<PresShell> presShell = docShell->GetPresShell()) {
+    if (nsIFrame* root = presShell->GetRootFrame()) {
+      root->SchedulePaint();
+    }
+  }
+}
+
+void BrowserChild::ReinitRendering() {
+  MOZ_ASSERT(mLayersId.IsValid());
+
+  // Before we establish a new PLayerTransaction, we must connect our layer tree
+  // id, CompositorBridge, and the widget compositor all together again.
+  // Normally this happens in BrowserParent before BrowserChild is given
+  // rendering information.
+  //
+  // In this case, we will send a sync message to our BrowserParent, which in
+  // turn will send a sync message to the Compositor of the widget owning this
+  // tab. This guarantees the correct association is in place before our
+  // PLayerTransaction constructor message arrives on the cross-process
+  // compositor bridge.
+  CompositorOptions options;
+  SendEnsureLayersConnected(&options);
+  mCompositorOptions = Some(options);
+
+  bool success = false;
+  RefPtr<CompositorBridgeChild> cb = CompositorBridgeChild::Get();
+
+  if (cb) {
+    success = CreateRemoteLayerManager(cb);
+  }
+
+  if (!success) {
+    NS_WARNING("failed to recreate layer manager");
+    return;
+  }
+
+  mLayersConnected = Some(true);
+  ImageBridgeChild::IdentifyCompositorTextureHost(mTextureFactoryIdentifier);
+  gfx::VRManagerChild::IdentifyTextureHost(mTextureFactoryIdentifier);
+
+  InitAPZState();
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+  lm->SetLayersObserverEpoch(mLayersObserverEpoch);
+
+  nsCOMPtr<Document> doc(GetTopLevelDocument());
+  doc->NotifyLayerManagerRecreated();
+}
+
+void BrowserChild::ReinitRenderingForDeviceReset() {
+  InvalidateLayers();
+
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  if (WebRenderLayerManager* wlm = lm->AsWebRenderLayerManager()) {
+    wlm->DoDestroy(/* aIsSync */ true);
+  } else if (ClientLayerManager* clm = lm->AsClientLayerManager()) {
+    if (ShadowLayerForwarder* fwd = clm->AsShadowForwarder()) {
+      // Force the LayerTransactionChild to synchronously shutdown. It is
+      // okay to do this early, we'll simply stop sending messages. This
+      // step is necessary since otherwise the compositor will think we
+      // are trying to attach two layer trees to the same ID.
+      fwd->SynchronouslyShutdown();
+    }
+  } else {
+    if (mLayersConnected.isNothing()) {
+      return;
+    }
+  }
+
+  // Proceed with destroying and recreating the layer manager.
+  ReinitRendering();
+}
+
+NS_IMETHODIMP
+BrowserChild::OnShowTooltip(int32_t aXCoords, int32_t aYCoords,
+                            const nsAString& aTipText,
+                            const nsAString& aTipDir) {
+  nsString str(aTipText);
+  nsString dir(aTipDir);
+  SendShowTooltip(aXCoords, aYCoords, str, dir);
+  return NS_OK;
+}
+
+NS_IMETHODIMP
+BrowserChild::OnHideTooltip() {
+  SendHideTooltip();
+  return NS_OK;
+}
+
+void BrowserChild::NotifyJankedAnimations(
+    const nsTArray<uint64_t>& aJankedAnimations) {
+  MOZ_ASSERT(mPuppetWidget);
+  RefPtr<LayerManager> lm = mPuppetWidget->GetLayerManager();
+  MOZ_ASSERT(lm);
+  lm->UpdatePartialPrerenderedAnimations(aJankedAnimations);
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvRequestNotifyAfterRemotePaint() {
+  // Get the CompositorBridgeChild instance for this content thread.
+  CompositorBridgeChild* compositor = CompositorBridgeChild::Get();
+
+  // Tell the CompositorBridgeChild that, when it gets a RemotePaintIsReady
+  // message that it should forward it us so that we can bounce it to our
+  // BrowserParent.
+  compositor->RequestNotifyAfterRemotePaint(this);
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvUIResolutionChanged(
+    const float& aDpi, const int32_t& aRounding, const double& aScale) {
+  nsCOMPtr<Document> document(GetTopLevelDocument());
+  if (!document) {
+    return IPC_OK();
+  }
+
+  ScreenIntSize oldScreenSize = GetInnerSize();
+  if (aDpi > 0) {
+    mPuppetWidget->UpdateBackingScaleCache(aDpi, aRounding, aScale);
+  }
+  RefPtr<nsPresContext> presContext = document->GetPresContext();
+  if (presContext) {
+    presContext->UIResolutionChangedSync();
+  }
+
+  ScreenIntSize screenSize = GetInnerSize();
+  if (mHasValidInnerSize && oldScreenSize != screenSize) {
+    ScreenIntRect screenRect = GetOuterRect();
+
+    // See RecvUpdateDimensions for the order of these operations.
+    nsCOMPtr<nsIBaseWindow> baseWin = do_QueryInterface(WebNavigation());
+    baseWin->SetPositionAndSize(0, 0, screenSize.width, screenSize.height,
+                                nsIBaseWindow::eRepaint);
+
+    mPuppetWidget->Resize(screenRect.x + mClientOffset.x + mChromeOffset.x,
+                          screenRect.y + mClientOffset.y + mChromeOffset.y,
+                          screenSize.width, screenSize.height, true);
+  }
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSafeAreaInsetsChanged(
+    const mozilla::ScreenIntMargin& aSafeAreaInsets) {
+  mPuppetWidget->UpdateSafeAreaInsets(aSafeAreaInsets);
+
+  nsCOMPtr<nsIScreenManager> screenMgr =
+      do_GetService("@mozilla.org/gfx/screenmanager;1");
+  ScreenIntMargin currentSafeAreaInsets;
+  if (screenMgr) {
+    // aSafeAreaInsets is for current screen. But we have to calculate
+    // safe insets for content window.
+    int32_t x, y, cx, cy;
+    GetDimensions(0, &x, &y, &cx, &cy);
+    nsCOMPtr<nsIScreen> screen;
+    screenMgr->ScreenForRect(x, y, cx, cy, getter_AddRefs(screen));
+
+    if (screen) {
+      LayoutDeviceIntRect windowRect(x + mClientOffset.x + mChromeOffset.x,
+                                     y + mClientOffset.y + mChromeOffset.y, cx,
+                                     cy);
+      currentSafeAreaInsets = nsContentUtils::GetWindowSafeAreaInsets(
+          screen, aSafeAreaInsets, windowRect);
+    }
+  }
+
+  if (nsCOMPtr<Document> document = GetTopLevelDocument()) {
+    nsPresContext* presContext = document->GetPresContext();
+    if (presContext) {
+      presContext->SetSafeAreaInsets(currentSafeAreaInsets);
+    }
+  }
+
+  // https://github.com/w3c/csswg-drafts/issues/4670
+  // Actually we don't set this value on sub document. This behaviour is
+  // same as Blink that safe area insets isn't set on sub document.
+
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvAllowScriptsToClose() {
+  nsCOMPtr<nsPIDOMWindowOuter> window = do_GetInterface(WebNavigation());
+  if (window) {
+    nsGlobalWindowOuter::Cast(window)->AllowScriptsToClose();
+  }
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvSetWidgetNativeData(
+    const WindowsHandle& aWidgetNativeData) {
+  mWidgetNativeData = aWidgetNativeData;
+  return IPC_OK();
+}
+
+mozilla::ipc::IPCResult BrowserChild::RecvReleaseAllPointerCapture() {
+  PointerEventHandler::ReleaseAllPointerCapture();
+  return IPC_OK();
+}
+
+mozilla::plugins::PPluginWidgetChild* BrowserChild::AllocPPluginWidgetChild() {
+#ifdef XP_WIN
+  return new mozilla::plugins::PluginWidgetChild();
+#else
+  MOZ_ASSERT_UNREACHABLE("AllocPPluginWidgetChild only supports Windows");
+  return nullptr;
+#endif
+}
+
+bool BrowserChild::DeallocPPluginWidgetChild(
+    mozilla::plugins::PPluginWidgetChild* aActor) {
+  delete aActor;
+  return true;
+}
+
+#ifdef XP_WIN
+nsresult BrowserChild::CreatePluginWidget(nsIWidget* aParent,
+                                          nsIWidget** aOut) {
+  *aOut = nullptr;
+  mozilla::plugins::PluginWidgetChild* child =
+      static_cast<mozilla::plugins::PluginWidgetChild*>(
+          SendPPluginWidgetConstructor());
+  if (!child) {
+    NS_ERROR("couldn't create PluginWidgetChild");
+    return NS_ERROR_UNEXPECTED;
+  }
+  nsCOMPtr<nsIWidget> pluginWidget =
+      nsIWidget::CreatePluginProxyWidget(this, child);
+  if (!pluginWidget) {
+    NS_ERROR("couldn't create PluginWidgetProxy");
+    return NS_ERROR_UNEXPECTED;
+  }
+
+  nsWidgetInitData initData;
+  initData.mWindowType = eWindowType_plugin_ipc_content;
+  initData.clipChildren = true;
+  initData.clipSiblings = true;
+  nsresult rv = pluginWidget->Create(
+      aParent, nullptr, LayoutDeviceIntRect(0, 0, 0, 0), &initData);
+  if (NS_FAILED(rv)) {
+    NS_WARNING("Creating native plugin widget on the chrome side failed.");
+  }
+  pluginWidget.forget(aOut);
+  return rv;
+}
+#endif  // XP_WIN
+
+PPaymentRequestChild* BrowserChild::AllocPPaymentRequestChild() {
+  MOZ_CRASH(
+      "We should never be manually allocating PPaymentRequestChild actors");
+  return nullptr;
+}
+
+bool BrowserChild::DeallocPPaymentRequestChild(PPaymentRequestChild* actor) {
+  delete actor;
+  return true;
+}
+
+ScreenIntSize BrowserChild::GetInnerSize() {
+  LayoutDeviceIntSize innerSize =
+      RoundedToInt(mUnscaledInnerSize * mPuppetWidget->GetDefaultScale());
+  return ViewAs<ScreenPixel>(
+      innerSize, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
+};
+
+Maybe<nsRect> BrowserChild::GetVisibleRect() const {
+  if (mIsTopLevel) {
+    // We are conservative about visible rects for top-level browsers to avoid
+    // artifacts when resizing
+    return Nothing();
+  }
+
+  return Some(mEffectsInfo.mVisibleRect);
+}
+
+Maybe<LayoutDeviceRect>
+BrowserChild::GetTopLevelViewportVisibleRectInSelfCoords() const {
+  if (mIsTopLevel) {
+    return Nothing();
+  }
+
+  if (!mChildToParentConversionMatrix) {
+    // We have no way to tell this remote document visible rect right now.
+    return Nothing();
+  }
+
+  Maybe<LayoutDeviceToLayoutDeviceMatrix4x4> inverse =
+      mChildToParentConversionMatrix->MaybeInverse();
+  if (!inverse) {
+    return Nothing();
+  }
+
+  // Convert the remote document visible rect to the coordinate system of the
+  // iframe document.
+  Maybe<LayoutDeviceRect> rect = UntransformBy(
+      *inverse,
+      ViewAs<LayoutDevicePixel>(
+          mTopLevelViewportVisibleRectInBrowserCoords,
+          PixelCastJustification::ContentProcessIsLayerInUiProcess),
+      LayoutDeviceRect::MaxIntRect());
+  if (!rect) {
+    return Nothing();
+  }
+
+  return rect;
+}
+
+ScreenIntRect BrowserChild::GetOuterRect() {
+  LayoutDeviceIntRect outerRect =
+      RoundedToInt(mUnscaledOuterRect * mPuppetWidget->GetDefaultScale());
+  return ViewAs<ScreenPixel>(
+      outerRect, PixelCastJustification::LayoutDeviceIsScreenForTabDims);
+}
+
+void BrowserChild::PaintWhileInterruptingJS(
+    const layers::LayersObserverEpoch& aEpoch) {
+  if (!IPCOpen() || !mPuppetWidget || !mPuppetWidget->HasLayerManager()) {
+    // Don't bother doing anything now. Better to wait until we receive the
+    // message on the PContent channel.
+    return;
+  }
+
+  MOZ_DIAGNOSTIC_ASSERT(nsContentUtils::IsSafeToRunScript());
+  nsAutoScriptBlocker scriptBlocker;
+  RecvRenderLayers(true /* aEnabled */, aEpoch);
+}
+
+nsresult BrowserChild::CanCancelContentJS(
+    nsIRemoteTab::NavigationType aNavigationType, int32_t aNavigationIndex,
+    nsIURI* aNavigationURI, int32_t aEpoch, bool* aCanCancel) {
+  nsresult rv;
+  *aCanCancel = false;
+
+  if (aEpoch <= mCancelContentJSEpoch) {
+    // The next page loaded before we got here, so we shouldn't try to cancel
+    // the content JS.
+    return NS_OK;
+  }
+
+  // If we have session history in the parent we've already performed
+  // the checks following, so we can return early.
+  if (mozilla::SessionHistoryInParent()) {
+    *aCanCancel = true;
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  nsCOMPtr<nsISHistory> history;
+  if (docShell) {
+    history = nsDocShell::Cast(docShell)->GetSessionHistory()->LegacySHistory();
+  }
+
+  if (!history) {
+    return NS_ERROR_FAILURE;
+  }
+
+  int32_t current;
+  rv = history->GetIndex(&current);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  if (current == -1) {
+    // This tab has no history! Just return.
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsISHEntry> entry;
+  rv = history->GetEntryAtIndex(current, getter_AddRefs(entry));
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  nsCOMPtr<nsIURI> currentURI = entry->GetURI();
+  if (!currentURI->SchemeIs("http") && !currentURI->SchemeIs("https") &&
+      !currentURI->SchemeIs("file")) {
+    // Only cancel content JS for http(s) and file URIs. Other URIs are probably
+    // internal and we should just let them run to completion.
+    return NS_OK;
+  }
+
+  if (aNavigationType == nsIRemoteTab::NAVIGATE_BACK) {
+    aNavigationIndex = current - 1;
+  } else if (aNavigationType == nsIRemoteTab::NAVIGATE_FORWARD) {
+    aNavigationIndex = current + 1;
+  } else if (aNavigationType == nsIRemoteTab::NAVIGATE_URL) {
+    if (!aNavigationURI) {
+      return NS_ERROR_FAILURE;
+    }
+
+    if (aNavigationURI->SchemeIs("javascript")) {
+      // "javascript:" URIs don't (necessarily) trigger navigation to a
+      // different page, so don't allow the current page's JS to terminate.
+      return NS_OK;
+    }
+
+    // If navigating directly to a URL (e.g. via hitting Enter in the location
+    // bar), then we can cancel anytime the next URL is different from the
+    // current, *excluding* the ref ("#").
+    bool equals;
+    rv = currentURI->EqualsExceptRef(aNavigationURI, &equals);
+    NS_ENSURE_SUCCESS(rv, rv);
+    *aCanCancel = !equals;
+    return NS_OK;
+  }
+  // Note: aNavigationType may also be NAVIGATE_INDEX, in which case we don't
+  // need to do anything special.
+
+  int32_t delta = aNavigationIndex > current ? 1 : -1;
+  for (int32_t i = current + delta; i != aNavigationIndex + delta; i += delta) {
+    nsCOMPtr<nsISHEntry> nextEntry;
+    // If `i` happens to be negative, this call will fail (which is what we
+    // would want to happen).
+    rv = history->GetEntryAtIndex(i, getter_AddRefs(nextEntry));
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    nsCOMPtr<nsISHEntry> laterEntry = delta == 1 ? nextEntry : entry;
+    nsCOMPtr<nsIURI> thisURI = entry->GetURI();
+    nsCOMPtr<nsIURI> nextURI = nextEntry->GetURI();
+
+    // If we changed origin and the load wasn't in a subframe, we know it was
+    // a full document load, so we can cancel the content JS safely.
+    if (!laterEntry->GetIsSubFrame()) {
+      nsAutoCString thisHost;
+      rv = thisURI->GetPrePath(thisHost);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      nsAutoCString nextHost;
+      rv = nextURI->GetPrePath(nextHost);
+      NS_ENSURE_SUCCESS(rv, rv);
+
+      if (!thisHost.Equals(nextHost)) {
+        *aCanCancel = true;
+        return NS_OK;
+      }
+    }
+
+    entry = nextEntry;
+  }
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::BeginSendingWebProgressEventsToParent() {
+  mShouldSendWebProgressEventsToParent = true;
+  return NS_OK;
+}
+
+nsresult BrowserChild::GetHasSiblings(bool* aHasSiblings) {
+  *aHasSiblings = mHasSiblings;
+  return NS_OK;
+}
+
+nsresult BrowserChild::SetHasSiblings(bool aHasSiblings) {
+  mHasSiblings = aHasSiblings;
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnStateChange(nsIWebProgress* aWebProgress,
+                                          nsIRequest* aRequest,
+                                          uint32_t aStateFlags,
+                                          nsresult aStatus) {
+  if (!IPCOpen() || !mShouldSendWebProgressEventsToParent) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(WebNavigation());
+  if (!docShell) {
+    return NS_OK;
+  }
+
+  // We shouldn't need to notify the parent of redirect state changes, since
+  // with DocumentChannel that only happens when we switch to the real channel,
+  // and that's an implementation detail that we can hide.
+  if (aStateFlags & nsIWebProgressListener::STATE_IS_REDIRECTED_DOCUMENT) {
+    return NS_OK;
+  }
+
+  RefPtr<Document> document;
+  if (nsCOMPtr<nsPIDOMWindowOuter> outerWindow = do_GetInterface(docShell)) {
+    document = outerWindow->GetExtantDoc();
+  } else {
+    return NS_OK;
+  }
+
+  Maybe<WebProgressData> webProgressData;
+  Maybe<WebProgressStateChangeData> stateChangeData;
+  RequestData requestData;
+
+  MOZ_TRY(PrepareProgressListenerData(aWebProgress, aRequest, webProgressData,
+                                      requestData));
+
+  if (webProgressData->isTopLevel()) {
+    stateChangeData.emplace();
+
+    stateChangeData->isNavigating() = docShell->GetIsNavigating();
+    stateChangeData->mayEnableCharacterEncodingMenu() =
+        docShell->GetMayEnableCharacterEncodingMenu();
+    stateChangeData->charsetAutodetected() = docShell->GetCharsetAutodetected();
+
+    if (document && aStateFlags & nsIWebProgressListener::STATE_STOP) {
+      document->GetContentType(stateChangeData->contentType());
+      document->GetCharacterSet(stateChangeData->charset());
+      stateChangeData->documentURI() = document->GetDocumentURIObject();
+    } else {
+      stateChangeData->contentType().SetIsVoid(true);
+      stateChangeData->charset().SetIsVoid(true);
+    }
+  }
+
+  Unused << SendOnStateChange(webProgressData, requestData, aStateFlags,
+                              aStatus, stateChangeData);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnProgressChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             int32_t aCurSelfProgress,
+                                             int32_t aMaxSelfProgress,
+                                             int32_t aCurTotalProgress,
+                                             int32_t aMaxTotalProgress) {
+  if (!IPCOpen() || !mShouldSendWebProgressEventsToParent) {
+    return NS_OK;
+  }
+
+  Maybe<WebProgressData> webProgressData;
+  RequestData requestData;
+
+  nsresult rv = PrepareProgressListenerData(aWebProgress, aRequest,
+                                            webProgressData, requestData);
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  Unused << SendOnProgressChange(webProgressData, requestData, aCurSelfProgress,
+                                 aMaxSelfProgress, aCurTotalProgress,
+                                 aMaxTotalProgress);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnLocationChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             nsIURI* aLocation,
+                                             uint32_t aFlags) {
+  if (!IPCOpen() || !mShouldSendWebProgressEventsToParent) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIWebNavigation> webNav = WebNavigation();
+  nsCOMPtr<nsIDocShell> docShell = do_GetInterface(webNav);
+  if (!docShell) {
+    return NS_OK;
+  }
+
+  RefPtr<Document> document;
+  if (nsCOMPtr<nsPIDOMWindowOuter> outerWindow = do_GetInterface(docShell)) {
+    document = outerWindow->GetExtantDoc();
+  } else {
+    return NS_OK;
+  }
+
+  if (!document) {
+    return NS_OK;
+  }
+
+  Maybe<WebProgressData> webProgressData;
+  RequestData requestData;
+
+  MOZ_TRY(PrepareProgressListenerData(aWebProgress, aRequest, webProgressData,
+                                      requestData));
+
+  Maybe<WebProgressLocationChangeData> locationChangeData;
+
+  bool canGoBack = false;
+  bool canGoForward = false;
+
+  MOZ_TRY(webNav->GetCanGoBack(&canGoBack));
+  MOZ_TRY(webNav->GetCanGoForward(&canGoForward));
+
+  if (aWebProgress && webProgressData->isTopLevel()) {
+    locationChangeData.emplace();
+
+    document->GetContentType(locationChangeData->contentType());
+    locationChangeData->isNavigating() = docShell->GetIsNavigating();
+    locationChangeData->documentURI() = document->GetDocumentURIObject();
+    document->GetTitle(locationChangeData->title());
+    document->GetCharacterSet(locationChangeData->charset());
+
+    locationChangeData->mayEnableCharacterEncodingMenu() =
+        docShell->GetMayEnableCharacterEncodingMenu();
+    locationChangeData->charsetAutodetected() =
+        docShell->GetCharsetAutodetected();
+
+    locationChangeData->contentPrincipal() = document->NodePrincipal();
+    locationChangeData->contentPartitionedPrincipal() =
+        document->PartitionedPrincipal();
+    locationChangeData->csp() = document->GetCsp();
+    locationChangeData->referrerInfo() = document->ReferrerInfo();
+    locationChangeData->isSyntheticDocument() = document->IsSyntheticDocument();
+
+    if (nsCOMPtr<nsILoadGroup> loadGroup = document->GetDocumentLoadGroup()) {
+      uint64_t requestContextID = 0;
+      MOZ_TRY(loadGroup->GetRequestContextID(&requestContextID));
+      locationChangeData->requestContextID() = Some(requestContextID);
+    }
+
+#ifdef MOZ_CRASHREPORTER
+    if (CrashReporter::GetEnabled()) {
+      nsCOMPtr<nsIURI> annotationURI;
+
+      nsresult rv =
+          NS_MutateURI(aLocation).SetUserPass(""_ns).Finalize(annotationURI);
+
+      if (NS_FAILED(rv)) {
+        // Ignore failures on about: URIs.
+        annotationURI = aLocation;
+      }
+
+      CrashReporter::AnnotateCrashReport(CrashReporter::Annotation::URL,
+                                         annotationURI->GetSpecOrDefault());
+    }
+#endif
+  }
+
+  Unused << SendOnLocationChange(webProgressData, requestData, aLocation,
+                                 aFlags, canGoBack, canGoForward,
+                                 locationChangeData);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnStatusChange(nsIWebProgress* aWebProgress,
+                                           nsIRequest* aRequest,
+                                           nsresult aStatus,
+                                           const char16_t* aMessage) {
+  if (!IPCOpen() || !mShouldSendWebProgressEventsToParent) {
+    return NS_OK;
+  }
+
+  Maybe<WebProgressData> webProgressData;
+  RequestData requestData;
+
+  nsresult rv = PrepareProgressListenerData(aWebProgress, aRequest,
+                                            webProgressData, requestData);
+
+  NS_ENSURE_SUCCESS(rv, rv);
+
+  const nsString message(aMessage);
+
+  Unused << SendOnStatusChange(webProgressData, requestData, aStatus, message);
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnSecurityChange(nsIWebProgress* aWebProgress,
+                                             nsIRequest* aRequest,
+                                             uint32_t aState) {
+  // Security changes are now handled entirely in the parent process
+  // so we don't need to worry about forwarding them (and we shouldn't
+  // be receiving any to forward).
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::OnContentBlockingEvent(nsIWebProgress* aWebProgress,
+                                                   nsIRequest* aRequest,
+                                                   uint32_t aEvent) {
+  // The OnContentBlockingEvent only happenes in the parent process. It should
+  // not be seen in the content process.
+  MOZ_DIAGNOSTIC_ASSERT(
+      false, "OnContentBlockingEvent should not be seen in content process.");
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP BrowserChild::OnProgressChange64(nsIWebProgress* aWebProgress,
+                                               nsIRequest* aRequest,
+                                               int64_t aCurSelfProgress,
+                                               int64_t aMaxSelfProgress,
+                                               int64_t aCurTotalProgress,
+                                               int64_t aMaxTotalProgress) {
+  // All the events we receive are filtered through an nsBrowserStatusFilter,
+  // which accepts ProgressChange64 events, but truncates the progress values to
+  // uint32_t and calls OnProgressChange.
+  return NS_ERROR_NOT_IMPLEMENTED;
+}
+
+NS_IMETHODIMP BrowserChild::OnRefreshAttempted(nsIWebProgress* aWebProgress,
+                                               nsIURI* aRefreshURI,
+                                               int32_t aMillis, bool aSameURI,
+                                               bool* aOut) {
+  NS_ENSURE_ARG_POINTER(aOut);
+  *aOut = true;
+
+  return NS_OK;
+}
+
+NS_IMETHODIMP BrowserChild::NotifyNavigationFinished() {
+  Unused << SendNavigationFinished();
+  return NS_OK;
+}
+
+nsresult BrowserChild::PrepareProgressListenerData(
+    nsIWebProgress* aWebProgress, nsIRequest* aRequest,
+    Maybe<WebProgressData>& aWebProgressData, RequestData& aRequestData) {
+  if (aWebProgress) {
+    aWebProgressData.emplace();
+
+    bool isTopLevel = false;
+    nsresult rv = aWebProgress->GetIsTopLevel(&isTopLevel);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aWebProgressData->isTopLevel() = isTopLevel;
+
+    bool isLoadingDocument = false;
+    rv = aWebProgress->GetIsLoadingDocument(&isLoadingDocument);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aWebProgressData->isLoadingDocument() = isLoadingDocument;
+
+    uint32_t loadType = 0;
+    rv = aWebProgress->GetLoadType(&loadType);
+    NS_ENSURE_SUCCESS(rv, rv);
+    aWebProgressData->loadType() = loadType;
+  }
+
+  nsCOMPtr<nsIChannel> channel = do_QueryInterface(aRequest);
+  if (channel) {
+    nsCOMPtr<nsIURI> uri;
+    nsresult rv = channel->GetURI(getter_AddRefs(uri));
+    NS_ENSURE_SUCCESS(rv, rv);
+    aRequestData.requestURI() = uri;
+
+    rv = channel->GetOriginalURI(getter_AddRefs(uri));
+    NS_ENSURE_SUCCESS(rv, rv);
+    aRequestData.originalRequestURI() = uri;
+
+    nsCOMPtr<nsIClassifiedChannel> classifiedChannel =
+        do_QueryInterface(channel);
+    if (classifiedChannel) {
+      nsAutoCString matchedList;
+      rv = classifiedChannel->GetMatchedList(matchedList);
+      NS_ENSURE_SUCCESS(rv, rv);
+      aRequestData.matchedList() = std::move(matchedList);
+    }
+  }
+  return NS_OK;
+}
+
+bool BrowserChild::UpdateSessionStore(uint32_t aFlushId, bool aIsFinal) {
+  if (!mSessionStoreListener) {
+    return false;
+  }
+  RefPtr<ContentSessionStore> store = mSessionStoreListener->GetSessionStore();
+
+  Maybe<nsCString> docShellCaps;
+  if (store->IsDocCapChanged()) {
+    docShellCaps.emplace(store->GetDocShellCaps());
+  }
+
+  Maybe<bool> privatedMode;
+  if (store->IsPrivateChanged()) {
+    privatedMode.emplace(store->GetPrivateModeEnabled());
+  }
+
+  nsTArray<int32_t> positionDescendants;
+  nsTArray<nsCString> positions;
+  if (store->IsScrollPositionChanged()) {
+    store->GetScrollPositions(positions, positionDescendants);
+  }
+
+  nsTArray<InputFormData> inputs;
+  nsTArray<CollectedInputDataValue> idVals, xPathVals;
+  if (store->IsFormDataChanged()) {
+    inputs = store->GetInputs(idVals, xPathVals);
+  }
+
+  nsTArray<nsCString> origins;
+  nsTArray<nsString> keys, values;
+  bool isFullStorage = false;
+  if (store->IsStorageUpdated()) {
+    isFullStorage = store->GetAndClearStorageChanges(origins, keys, values);
+  }
+
+  Unused << SendSessionStoreUpdate(
+      docShellCaps, privatedMode, positions, positionDescendants, inputs,
+      idVals, xPathVals, origins, keys, values, isFullStorage,
+      store->GetAndClearSHistoryChanged(), aFlushId, aIsFinal,
+      mSessionStoreListener->GetEpoch());
+  return true;
+}
+
+#ifdef XP_WIN
+RefPtr<PBrowserChild::IsWindowSupportingProtectedMediaPromise>
+BrowserChild::DoesWindowSupportProtectedMedia() {
+  MOZ_ASSERT(
+      NS_IsMainThread(),
+      "Protected media support check should be done on main thread only.");
+  if (mWindowSupportsProtectedMedia) {
+    // If we've already checked and have a cached result, resolve with that.
+    return IsWindowSupportingProtectedMediaPromise::CreateAndResolve(
+        mWindowSupportsProtectedMedia.value(), __func__);
+  }
+  RefPtr<BrowserChild> self = this;
+  // We chain off the promise rather than passing it directly so we can cache
+  // the result and use that for future calls.
+  return SendIsWindowSupportingProtectedMedia(ChromeOuterWindowID())
+      ->Then(
+          GetCurrentSerialEventTarget(), __func__,
+          [self](bool isSupported) {
+            // If a result was cached while this check was inflight, ensure the
+            // results match.
+            MOZ_ASSERT_IF(
+                self->mWindowSupportsProtectedMedia,
+                self->mWindowSupportsProtectedMedia.value() == isSupported);
+            // Cache the response as it will not change during the lifetime
+            // of this object.
+            self->mWindowSupportsProtectedMedia = Some(isSupported);
+            return IsWindowSupportingProtectedMediaPromise::CreateAndResolve(
+                self->mWindowSupportsProtectedMedia.value(), __func__);
+          },
+          [](ResponseRejectReason reason) {
+            return IsWindowSupportingProtectedMediaPromise::CreateAndReject(
+                reason, __func__);
+          });
+}
+#endif
+
+void BrowserChild::NotifyContentBlockingEvent(
+    uint32_t aEvent, nsIChannel* aChannel, bool aBlocked,
+    const nsACString& aTrackingOrigin,
+    const nsTArray<nsCString>& aTrackingFullHashes,
+    const Maybe<
+        mozilla::ContentBlockingNotifier::StorageAccessPermissionGrantedReason>&
+        aReason) {
+  if (!IPCOpen()) {
+    return;
+  }
+
+  Maybe<WebProgressData> webProgressData;
+  RequestData requestData;
+  nsresult rv = PrepareProgressListenerData(nullptr, aChannel, webProgressData,
+                                            requestData);
+  NS_ENSURE_SUCCESS_VOID(rv);
+
+  Unused << SendNotifyContentBlockingEvent(aEvent, requestData, aBlocked,
+                                           PromiseFlatCString(aTrackingOrigin),
+                                           aTrackingFullHashes, aReason);
+}
+
+BrowserChildMessageManager::BrowserChildMessageManager(
+    BrowserChild* aBrowserChild)
+    : ContentFrameMessageManager(new nsFrameMessageManager(aBrowserChild)),
+      mBrowserChild(aBrowserChild) {}
+
+BrowserChildMessageManager::~BrowserChildMessageManager() = default;
+
+NS_IMPL_CYCLE_COLLECTION_CLASS(BrowserChildMessageManager)
+
+NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN_INHERITED(BrowserChildMessageManager,
+                                                DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mMessageManager);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK(mBrowserChild);
+  NS_IMPL_CYCLE_COLLECTION_UNLINK_WEAK_REFERENCE
+NS_IMPL_CYCLE_COLLECTION_UNLINK_END
+
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(BrowserChildMessageManager,
+                                                  DOMEventTargetHelper)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mMessageManager)
+  NS_IMPL_CYCLE_COLLECTION_TRAVERSE(mBrowserChild)
+NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END
+
+NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(BrowserChildMessageManager)
+  NS_INTERFACE_MAP_ENTRY(nsIMessageSender)
+  NS_INTERFACE_MAP_ENTRY(ContentFrameMessageManager)
+  NS_INTERFACE_MAP_ENTRY(nsISupportsWeakReference)
+NS_INTERFACE_MAP_END_INHERITING(DOMEventTargetHelper)
+
+NS_IMPL_ADDREF_INHERITED(BrowserChildMessageManager, DOMEventTargetHelper)
+NS_IMPL_RELEASE_INHERITED(BrowserChildMessageManager, DOMEventTargetHelper)
+
+JSObject* BrowserChildMessageManager::WrapObject(
+    JSContext* aCx, JS::Handle<JSObject*> aGivenProto) {
+  return ContentFrameMessageManager_Binding::Wrap(aCx, this, aGivenProto);
+}
+
+void BrowserChildMessageManager::MarkForCC() {
+  if (mBrowserChild) {
+    mBrowserChild->MarkScopesForCC();
+  }
+  EventListenerManager* elm = GetExistingListenerManager();
+  if (elm) {
+    elm->MarkForCC();
+  }
+  MessageManagerGlobal::MarkForCC();
+}
+
+Nullable<WindowProxyHolder> BrowserChildMessageManager::GetContent(
+    ErrorResult& aError) {
+  nsCOMPtr<nsIDocShell> docShell = GetDocShell(aError);
+  if (!docShell) {
+    return nullptr;
+  }
+  return WindowProxyHolder(docShell->GetBrowsingContext());
+}
+
+already_AddRefed<nsIDocShell> BrowserChildMessageManager::GetDocShell(
+    ErrorResult& aError) {
+  if (!mBrowserChild) {
+    aError.Throw(NS_ERROR_NULL_POINTER);
+    return nullptr;
+  }
+  nsCOMPtr<nsIDocShell> window =
+      do_GetInterface(mBrowserChild->WebNavigation());
+  return window.forget();
+}
+
+already_AddRefed<nsIEventTarget>
+BrowserChildMessageManager::GetTabEventTarget() {
+  nsCOMPtr<nsIEventTarget> target = EventTargetFor(TaskCategory::Other);
+  return target.forget();
+}
+
+nsresult BrowserChildMessageManager::Dispatch(
+    TaskCategory aCategory, already_AddRefed<nsIRunnable>&& aRunnable) {
+  return DispatcherTrait::Dispatch(aCategory, std::move(aRunnable));
+}
+
+nsISerialEventTarget* BrowserChildMessageManager::EventTargetFor(
+    TaskCategory aCategory) const {
+  return DispatcherTrait::EventTargetFor(aCategory);
+}
+
+AbstractThread* BrowserChildMessageManager::AbstractMainThreadFor(
+    TaskCategory aCategory) {
+  return DispatcherTrait::AbstractMainThreadFor(aCategory);
+}