Bug 1858610 - Move HandleTap from the APZCTreeManager to the InputBridge protocol. r=botond

The HandleTap message should be part of the InputBridge protocol to
ensure that the synthesized click events are sent to content after the
corresponding touch-end.

Differential Revision: https://phabricator.services.mozilla.com/D203468

gfx/layers/apz/test/mochitest/test_group_pointerevents.html

@@ -24,14 +24,13 @@ https://bugzilla.mozilla.org/show_bug.cgi?id=1285070
     {"file": "helper_bug1682170_pointercancel_on_touchaction_pinchzoom.html",
      "prefs": touch_action_prefs},
     {"file": "helper_bug1719855_pointercancel_on_touchmove_after_contextmenu_prevented.html"},
-  ];
-  if (getPlatform() != "android") {
-    // Bug 1858610: these subtests are flaky on Android.
-    subtests.push(
     {"file": "helper_bug1285070.html"},
     {"file": "helper_bug1299195.html", "prefs": [["dom.meta-viewport.enabled", isMac]]},
-      {"file": "helper_bug1502010_unconsumed_pan.html"}
+  ];
-    )
+
+  if (getPlatform() != "android") {
+    // Bug 1858610: these subtests are flaky on Android.
+    subtests.push({"file": "helper_bug1502010_unconsumed_pan.html"});
   }
 
   if (isApzEnabled()) {

gfx/layers/ipc/APZCTreeManagerChild.cpp

@@ -31,6 +31,9 @@ void APZCTreeManagerChild::SetCompositorSession(
   // we're setting mCompositorSession or we're clearing it).
   MOZ_ASSERT(!mCompositorSession ^ !aSession);
   mCompositorSession = aSession;
+  if (mInputBridge) {
+    mInputBridge->SetCompositorSession(aSession);
+  }
 }
 
 void APZCTreeManagerChild::SetInputBridge(APZInputBridgeChild* aInputBridge) {
@@ -143,45 +146,6 @@ void APZCTreeManagerChild::ActorDestroy(ActorDestroyReason aWhy) {
   mIPCOpen = false;
 }
 
-mozilla::ipc::IPCResult APZCTreeManagerChild::RecvHandleTap(
-    const TapType& aType, const LayoutDevicePoint& aPoint,
-    const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
-    const uint64_t& aInputBlockId,
-    const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics) {
-  MOZ_ASSERT(XRE_IsParentProcess());
-  if (mCompositorSession &&
-      mCompositorSession->RootLayerTreeId() == aGuid.mLayersId &&
-      mCompositorSession->GetContentController()) {
-    RefPtr<GeckoContentController> controller =
-        mCompositorSession->GetContentController();
-    controller->HandleTap(aType, aPoint, aModifiers, aGuid, aInputBlockId,
-                          aDoubleTapToZoomMetrics);
-    return IPC_OK();
-  }
-  dom::BrowserParent* tab =
-      dom::BrowserParent::GetBrowserParentFromLayersId(aGuid.mLayersId);
-  if (tab) {
-#ifdef MOZ_WIDGET_ANDROID
-    // On Android, touch events are dispatched from the UI thread to the main
-    // thread using the Android priority queue. It is possible that this tap has
-    // made it to the GPU process and back before they have been processed. We
-    // must therefore dispatch this message to the same queue, otherwise the tab
-    // may receive the tap event before the touch events that synthesized it.
-    mozilla::jni::DispatchToGeckoPriorityQueue(
-        NewRunnableMethod<TapType, LayoutDevicePoint, Modifiers,
-                          ScrollableLayerGuid, uint64_t,
-                          Maybe<DoubleTapToZoomMetrics>>(
-            "dom::BrowserParent::SendHandleTap", tab,
-            &dom::BrowserParent::SendHandleTap, aType, aPoint, aModifiers,
-            aGuid, aInputBlockId, aDoubleTapToZoomMetrics));
-#else
-    tab->SendHandleTap(aType, aPoint, aModifiers, aGuid, aInputBlockId,
-                       aDoubleTapToZoomMetrics);
-#endif
-  }
-  return IPC_OK();
-}
-
 mozilla::ipc::IPCResult APZCTreeManagerChild::RecvNotifyPinchGesture(
     const PinchGestureType& aType, const ScrollableLayerGuid& aGuid,
     const LayoutDevicePoint& aFocusPoint, const LayoutDeviceCoord& aSpanChange,

gfx/layers/ipc/APZCTreeManagerChild.h

@@ -73,13 +73,6 @@ class APZCTreeManagerChild : public IAPZCTreeManager,
   void ActorDestroy(ActorDestroyReason aWhy) override;
 
  protected:
-  MOZ_CAN_RUN_SCRIPT_BOUNDARY
-  mozilla::ipc::IPCResult RecvHandleTap(
-      const TapType& aType, const LayoutDevicePoint& aPoint,
-      const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
-      const uint64_t& aInputBlockId,
-      const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics);
-
   mozilla::ipc::IPCResult RecvNotifyPinchGesture(
       const PinchGestureType& aType, const ScrollableLayerGuid& aGuid,
       const LayoutDevicePoint& aFocusPoint,

gfx/layers/ipc/APZInputBridgeChild.cpp

@@ -12,6 +12,14 @@
 #include "mozilla/layers/APZThreadUtils.h"
 #include "mozilla/layers/SynchronousTask.h"
 
+#include "mozilla/layers/GeckoContentController.h"  // for GeckoContentController
+#include "mozilla/layers/DoubleTapToZoom.h"  // for DoubleTapToZoomMetrics
+#include "mozilla/layers/RemoteCompositorSession.h"  // for RemoteCompositorSession
+#include "mozilla/dom/BrowserParent.h"               // for BrowserParent
+#ifdef MOZ_WIDGET_ANDROID
+#  include "mozilla/jni/Utils.h"  // for DispatchToGeckoPriorityQueue
+#endif
+
 namespace mozilla {
 namespace layers {
 
@@ -31,13 +39,20 @@ RefPtr<APZInputBridgeChild> APZInputBridgeChild::Create(
 }
 
 APZInputBridgeChild::APZInputBridgeChild(const uint64_t& aProcessToken)
-    : mIsOpen(false), mProcessToken(aProcessToken) {
+    : mIsOpen(false),
+      mProcessToken(aProcessToken),
+      mCompositorSession(nullptr) {
   MOZ_ASSERT(XRE_IsParentProcess());
   MOZ_ASSERT(NS_IsMainThread());
 }
 
 APZInputBridgeChild::~APZInputBridgeChild() = default;
 
+void APZInputBridgeChild::SetCompositorSession(
+    RemoteCompositorSession* aSession) {
+  mCompositorSession = aSession;
+}
+
 void APZInputBridgeChild::Open(Endpoint<PAPZInputBridgeChild>&& aEndpoint) {
   APZThreadUtils::AssertOnControllerThread();
 
@@ -176,6 +191,63 @@ APZEventResult APZInputBridgeChild::ReceiveInputEvent(
   return res;
 }
 
+void APZInputBridgeChild::HandleTapOnMainThread(
+    const TapType& aType, const LayoutDevicePoint& aPoint,
+    const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId,
+    const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics) {
+  if (mCompositorSession &&
+      mCompositorSession->RootLayerTreeId() == aGuid.mLayersId &&
+      mCompositorSession->GetContentController()) {
+    RefPtr<GeckoContentController> controller =
+        mCompositorSession->GetContentController();
+    controller->HandleTap(aType, aPoint, aModifiers, aGuid, aInputBlockId,
+                          aDoubleTapToZoomMetrics);
+    return;
+  }
+  dom::BrowserParent* tab =
+      dom::BrowserParent::GetBrowserParentFromLayersId(aGuid.mLayersId);
+  if (tab) {
+#ifdef MOZ_WIDGET_ANDROID
+    // On Android, touch events are dispatched from the UI thread to the main
+    // thread using the Android priority queue. It is possible that this tap has
+    // made it to the GPU process and back before they have been processed. We
+    // must therefore dispatch this message to the same queue, otherwise the tab
+    // may receive the tap event before the touch events that synthesized it.
+    mozilla::jni::DispatchToGeckoPriorityQueue(
+        NewRunnableMethod<TapType, LayoutDevicePoint, Modifiers,
+                          ScrollableLayerGuid, uint64_t,
+                          Maybe<DoubleTapToZoomMetrics>>(
+            "dom::BrowserParent::SendHandleTap", tab,
+            &dom::BrowserParent::SendHandleTap, aType, aPoint, aModifiers,
+            aGuid, aInputBlockId, aDoubleTapToZoomMetrics));
+#else
+    tab->SendHandleTap(aType, aPoint, aModifiers, aGuid, aInputBlockId,
+                       aDoubleTapToZoomMetrics);
+#endif
+  }
+}
+
+mozilla::ipc::IPCResult APZInputBridgeChild::RecvHandleTap(
+    const TapType& aType, const LayoutDevicePoint& aPoint,
+    const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
+    const uint64_t& aInputBlockId,
+    const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics) {
+  if (NS_IsMainThread()) {
+    HandleTapOnMainThread(aType, aPoint, aModifiers, aGuid, aInputBlockId,
+                          aDoubleTapToZoomMetrics);
+  } else {
+    NS_DispatchToMainThread(
+        NewRunnableMethod<TapType, LayoutDevicePoint, Modifiers,
+                          ScrollableLayerGuid, uint64_t,
+                          Maybe<DoubleTapToZoomMetrics>>(
+            "layers::APZInputBridgeChild::HandleTapOnMainThread", this,
+            &APZInputBridgeChild::HandleTapOnMainThread, aType, aPoint,
+            aModifiers, aGuid, aInputBlockId, aDoubleTapToZoomMetrics));
+  }
+  return IPC_OK();
+}
+
 mozilla::ipc::IPCResult APZInputBridgeChild::RecvCallInputBlockCallback(
     uint64_t aInputBlockId, const APZHandledResult& aHandledResult) {
   auto it = mInputBlockCallbacks.find(aInputBlockId);

gfx/layers/ipc/APZInputBridgeChild.h

@@ -10,11 +10,16 @@
 #include "mozilla/layers/APZInputBridge.h"
 #include "mozilla/layers/PAPZInputBridgeChild.h"
 
+#include "mozilla/layers/GeckoContentControllerTypes.h"
+
 namespace mozilla {
 namespace layers {
 
+class RemoteCompositorSession;
+
 class APZInputBridgeChild : public PAPZInputBridgeChild, public APZInputBridge {
   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(APZInputBridgeChild, final)
+  using TapType = GeckoContentController_TapType;
 
  public:
   static RefPtr<APZInputBridgeChild> Create(
@@ -23,10 +28,19 @@ class APZInputBridgeChild : public PAPZInputBridgeChild, public APZInputBridge {
 
   void Destroy();
 
+  void SetCompositorSession(RemoteCompositorSession* aSession);
+
   APZEventResult ReceiveInputEvent(
       InputData& aEvent,
       InputBlockCallback&& aCallback = InputBlockCallback()) override;
 
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  mozilla::ipc::IPCResult RecvHandleTap(
+      const TapType& aType, const LayoutDevicePoint& aPoint,
+      const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
+      const uint64_t& aInputBlockId,
+      const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics);
+
   mozilla::ipc::IPCResult RecvCallInputBlockCallback(
       uint64_t aInputBlockId, const APZHandledResult& handledResult);
 
@@ -48,8 +62,16 @@ class APZInputBridgeChild : public PAPZInputBridgeChild, public APZInputBridge {
  private:
   void Open(Endpoint<PAPZInputBridgeChild>&& aEndpoint);
 
+  MOZ_CAN_RUN_SCRIPT_BOUNDARY
+  void HandleTapOnMainThread(
+      const TapType& aType, const LayoutDevicePoint& aPoint,
+      const Modifiers& aModifiers, const ScrollableLayerGuid& aGuid,
+      const uint64_t& aInputBlockId,
+      const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics);
+
   bool mIsOpen;
   uint64_t mProcessToken;
+  MOZ_NON_OWNING_REF RemoteCompositorSession* mCompositorSession = nullptr;
 
   using InputBlockCallbackMap =
       std::unordered_map<uint64_t, InputBlockCallback>;

gfx/layers/ipc/APZInputBridgeParent.cpp

@@ -16,14 +16,15 @@ namespace mozilla {
 namespace layers {
 
 /* static */
-RefPtr<APZInputBridgeParent> APZInputBridgeParent::Create(
+APZInputBridgeParent* APZInputBridgeParent::Create(
     const LayersId& aLayersId, Endpoint<PAPZInputBridgeParent>&& aEndpoint) {
-  RefPtr<APZInputBridgeParent> parent = new APZInputBridgeParent(aLayersId);
+  APZInputBridgeParent* parent = new APZInputBridgeParent(aLayersId);
   if (!aEndpoint.Bind(parent)) {
     // We can't recover from this.
     MOZ_CRASH("Failed to bind APZInputBridgeParent to endpoint");
   }
 
+  CompositorBridgeParent::SetAPZInputBridgeParent(aLayersId, parent);
   return parent;
 }
 
@@ -31,6 +32,7 @@ APZInputBridgeParent::APZInputBridgeParent(const LayersId& aLayersId) {
   MOZ_ASSERT(XRE_IsGPUProcess());
   MOZ_ASSERT(NS_IsMainThread());
 
+  mLayersId = aLayersId;
   mTreeManager = CompositorBridgeParent::GetAPZCTreeManager(aLayersId);
   MOZ_ASSERT(mTreeManager);
 }
@@ -205,6 +207,10 @@ mozilla::ipc::IPCResult APZInputBridgeParent::RecvProcessUnhandledEvent(
 }
 
 void APZInputBridgeParent::ActorDestroy(ActorDestroyReason aWhy) {
+  StaticMonitorAutoLock lock(CompositorBridgeParent::sIndirectLayerTreesLock);
+  CompositorBridgeParent::LayerTreeState& state =
+      CompositorBridgeParent::sIndirectLayerTrees[mLayersId];
+  state.mApzInputBridgeParent = nullptr;
   // We shouldn't need it after this
   mTreeManager = nullptr;
 }

gfx/layers/ipc/APZInputBridgeParent.h

@@ -18,7 +18,7 @@ class APZInputBridgeParent : public PAPZInputBridgeParent {
   NS_INLINE_DECL_REFCOUNTING(APZInputBridgeParent, final)
 
  public:
-  static RefPtr<APZInputBridgeParent> Create(
+  static APZInputBridgeParent* Create(
       const LayersId& aLayersId, Endpoint<PAPZInputBridgeParent>&& aEndpoint);
 
   mozilla::ipc::IPCResult RecvReceiveMultiTouchInputEvent(
@@ -67,6 +67,7 @@ class APZInputBridgeParent : public PAPZInputBridgeParent {
 
  private:
   RefPtr<IAPZCTreeManager> mTreeManager;
+  LayersId mLayersId;
 };
 
 }  // namespace layers

gfx/layers/ipc/CompositorBridgeParent.cpp

@@ -167,6 +167,7 @@ bool CompositorBridgeParentBase::DeallocShmem(ipc::Shmem& aShmem) {
 
 CompositorBridgeParent::LayerTreeState::LayerTreeState()
     : mApzcTreeManagerParent(nullptr),
+      mApzInputBridgeParent(nullptr),
       mParent(nullptr),
       mContentCompositorBridgeParent(nullptr) {}
 
@@ -645,9 +646,21 @@ bool CompositorBridgeParent::DeallocPAPZCTreeManagerParent(
   return true;
 }
 
+void CompositorBridgeParent::SetAPZInputBridgeParent(
+    const LayersId& aLayersId, APZInputBridgeParent* aInputBridgeParent) {
+  MOZ_RELEASE_ASSERT(XRE_IsGPUProcess());
+  MOZ_ASSERT(NS_IsMainThread());
+  StaticMonitorAutoLock lock(CompositorBridgeParent::sIndirectLayerTreesLock);
+  CompositorBridgeParent::LayerTreeState& state =
+      CompositorBridgeParent::sIndirectLayerTrees[aLayersId];
+  MOZ_ASSERT(!state.mApzInputBridgeParent);
+  state.mApzInputBridgeParent = aInputBridgeParent;
+}
+
 void CompositorBridgeParent::AllocateAPZCTreeManagerParent(
     const StaticMonitorAutoLock& aProofOfLayerTreeStateLock,
     const LayersId& aLayersId, LayerTreeState& aState) {
+  MOZ_ASSERT(CompositorThreadHolder::IsInCompositorThread());
   MOZ_ASSERT(aState.mParent == this);
   MOZ_ASSERT(mApzcTreeManager);
   MOZ_ASSERT(mApzUpdater);
@@ -1712,6 +1725,15 @@ APZCTreeManagerParent* CompositorBridgeParent::GetApzcTreeManagerParentForRoot(
   return state ? state->mApzcTreeManagerParent : nullptr;
 }
 
+/* static */
+APZInputBridgeParent* CompositorBridgeParent::GetApzInputBridgeParentForRoot(
+    LayersId aContentLayersId) {
+  StaticMonitorAutoLock lock(sIndirectLayerTreesLock);
+  CompositorBridgeParent::LayerTreeState* state =
+      GetStateForRoot(aContentLayersId, lock);
+  return state ? state->mApzInputBridgeParent : nullptr;
+}
+
 /* static */
 GeckoContentController*
 CompositorBridgeParent::GetGeckoContentControllerForRoot(

gfx/layers/ipc/CompositorBridgeParent.h

@@ -24,6 +24,7 @@
 #include "mozilla/layers/ISurfaceAllocator.h"  // for IShmemAllocator
 #include "mozilla/layers/LayersTypes.h"
 #include "mozilla/layers/PCompositorBridgeParent.h"
+#include "mozilla/layers/APZInputBridgeParent.h"
 #include "mozilla/webrender/WebRenderTypes.h"
 
 namespace mozilla {
@@ -394,6 +395,10 @@ class CompositorBridgeParent final : public CompositorBridgeParentBase,
     ~LayerTreeState();
     RefPtr<GeckoContentController> mController;
     APZCTreeManagerParent* mApzcTreeManagerParent;
+    // The mApzInputBridgeParent is only populated for LayerTreeState
+    // objects corresponding to root LayerIds (one for each top-level
+    // window).
+    APZInputBridgeParent* mApzInputBridgeParent;
     RefPtr<CompositorBridgeParent> mParent;
     RefPtr<WebRenderBridgeParent> mWrBridge;
     // Pointer to the ContentCompositorBridgeParent. Used by APZCs to share
@@ -437,6 +442,13 @@ class CompositorBridgeParent final : public CompositorBridgeParentBase,
   static GeckoContentController* GetGeckoContentControllerForRoot(
       LayersId aContentLayersId);
 
+  /**
+   * Same as the GetApzcTreeManagerParentForRoot function, but returns
+   * the APZInputBridge for the parent process.
+   */
+  static APZInputBridgeParent* GetApzInputBridgeParentForRoot(
+      LayersId aContentLayersId);
+
   /**
    * Used by the profiler to denote when a vsync occured
    */
@@ -454,6 +466,9 @@ class CompositorBridgeParent final : public CompositorBridgeParentBase,
       const StaticMonitorAutoLock& aProofOfLayerTreeStateLock,
       const LayersId& aLayersId, LayerTreeState& aLayerTreeStateToUpdate);
 
+  static void SetAPZInputBridgeParent(const LayersId& aLayersId,
+                                      APZInputBridgeParent* aInputBridgeParent);
+
   PAPZParent* AllocPAPZParent(const LayersId& aLayersId) override;
   bool DeallocPAPZParent(PAPZParent* aActor) override;
 

gfx/layers/ipc/PAPZCTreeManager.ipdl

@@ -80,10 +80,6 @@ parent:
 
 child:
 
-  async HandleTap(GeckoContentController_TapType aType, LayoutDevicePoint point, Modifiers aModifiers,
-                  ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
-                  DoubleTapToZoomMetrics? aDoubleTapToZoomMetrics);
-
   async NotifyPinchGesture(PinchGestureType aType, ScrollableLayerGuid aGuid,
                            LayoutDevicePoint aFocusPoint, LayoutDeviceCoord aSpanChange,
                            Modifiers aModifiers);

gfx/layers/ipc/PAPZInputBridge.ipdl

@@ -6,11 +6,15 @@
 include "ipc/nsGUIEventIPC.h";
 
 using mozilla::LayoutDeviceIntPoint from "Units.h";
+using mozilla::LayoutDevicePoint from "Units.h";
+using mozilla::layers::GeckoContentController_TapType from "mozilla/layers/GeckoContentControllerTypes.h";
+using mozilla::layers::DoubleTapToZoomMetrics from "mozilla/layers/DoubleTapToZoom.h";
 using struct mozilla::layers::ScrollableLayerGuid from "mozilla/layers/ScrollableLayerGuid.h";
 using struct mozilla::layers::APZEventResult from "mozilla/layers/APZInputBridge.h";
 using struct mozilla::layers::APZHandledResult from "mozilla/layers/APZInputBridge.h";
 
 using mozilla::EventMessage from "mozilla/EventForwards.h";
+using mozilla::Modifiers from "mozilla/EventForwards.h";
 using class mozilla::MultiTouchInput from "InputData.h";
 using class mozilla::MouseInput from "InputData.h";
 using class mozilla::PanGestureInput from "InputData.h";
@@ -82,6 +86,10 @@ parent:
 child:
   async CallInputBlockCallback(uint64_t aInputBlockId,
                                APZHandledResult aHandledResult);
+
+  async HandleTap(GeckoContentController_TapType aType, LayoutDevicePoint point,
+                  Modifiers aModifiers, ScrollableLayerGuid aGuid,
+                  uint64_t aInputBlockId, DoubleTapToZoomMetrics? aDoubleTapToZoomMetrics);
 };
 
 } // namespace gfx

gfx/layers/ipc/RemoteContentController.cpp

@@ -62,7 +62,7 @@ void RemoteContentController::RequestContentRepaint(
   }
 }
 
-void RemoteContentController::HandleTapOnMainThread(
+void RemoteContentController::HandleTapOnParentProcessMainThread(
     TapType aTapType, LayoutDevicePoint aPoint, Modifiers aModifiers,
     ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
     const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics) {
@@ -78,19 +78,18 @@ void RemoteContentController::HandleTapOnMainThread(
   }
 }
 
-void RemoteContentController::HandleTapOnCompositorThread(
+void RemoteContentController::HandleTapOnGPUProcessMainThread(
     TapType aTapType, LayoutDevicePoint aPoint, Modifiers aModifiers,
     ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
     const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics) {
   MOZ_ASSERT(XRE_IsGPUProcess());
-  MOZ_ASSERT(mCompositorThread->IsOnCurrentThread());
+  MOZ_ASSERT(NS_IsMainThread());
 
-  // The raw pointer to APZCTreeManagerParent is ok here because we are on
+  // Send a message to the controller thread to handle the single-tap gesture.
-  // the compositor thread.
+  APZInputBridgeParent* apzib =
-  APZCTreeManagerParent* apzctmp =
+      CompositorBridgeParent::GetApzInputBridgeParentForRoot(aGuid.mLayersId);
-      CompositorBridgeParent::GetApzcTreeManagerParentForRoot(aGuid.mLayersId);
+  if (apzib) {
-  if (apzctmp) {
+    Unused << apzib->SendHandleTap(aTapType, aPoint, aModifiers, aGuid,
-    Unused << apzctmp->SendHandleTap(aTapType, aPoint, aModifiers, aGuid,
                                    aInputBlockId, aDoubleTapToZoomMetrics);
   }
 }
@@ -103,17 +102,16 @@ void RemoteContentController::HandleTap(
   APZThreadUtils::AssertOnControllerThread();
 
   if (XRE_GetProcessType() == GeckoProcessType_GPU) {
-    if (mCompositorThread->IsOnCurrentThread()) {
+    if (NS_IsMainThread()) {
-      HandleTapOnCompositorThread(aTapType, aPoint, aModifiers, aGuid,
+      HandleTapOnGPUProcessMainThread(aTapType, aPoint, aModifiers, aGuid,
                                       aInputBlockId, aDoubleTapToZoomMetrics);
     } else {
-      // We have to send messages from the compositor thread
+      NS_DispatchToMainThread(NewRunnableMethod<TapType, LayoutDevicePoint,
-      mCompositorThread->Dispatch(
+                                                Modifiers, ScrollableLayerGuid,
-          NewRunnableMethod<TapType, LayoutDevicePoint, Modifiers,
+                                                uint64_t,
-                            ScrollableLayerGuid, uint64_t,
                                                 Maybe<DoubleTapToZoomMetrics>>(
-              "layers::RemoteContentController::HandleTapOnCompositorThread",
+          "layers::RemoteContentController::HandleTapOnGPUProcessMainThread",
-              this, &RemoteContentController::HandleTapOnCompositorThread,
+          this, &RemoteContentController::HandleTapOnGPUProcessMainThread,
           aTapType, aPoint, aModifiers, aGuid, aInputBlockId,
           aDoubleTapToZoomMetrics));
     }
@@ -123,8 +121,8 @@ void RemoteContentController::HandleTap(
   MOZ_ASSERT(XRE_IsParentProcess());
 
   if (NS_IsMainThread()) {
-    HandleTapOnMainThread(aTapType, aPoint, aModifiers, aGuid, aInputBlockId,
+    HandleTapOnParentProcessMainThread(aTapType, aPoint, aModifiers, aGuid,
-                          aDoubleTapToZoomMetrics);
+                                       aInputBlockId, aDoubleTapToZoomMetrics);
   } else {
     // We must be on Android, running on the Java UI thread
 #ifndef MOZ_WIDGET_ANDROID
@@ -138,13 +136,15 @@ void RemoteContentController::HandleTap(
     // using NS_DispatchToMainThread would post to a different message loop,
     // and introduces the possibility of this tap event getting processed
     // out of order with respect to the touch events that synthesized it.
-    mozilla::jni::DispatchToGeckoPriorityQueue(
+    mozilla::jni::DispatchToGeckoPriorityQueue(NewRunnableMethod<
-        NewRunnableMethod<TapType, LayoutDevicePoint, Modifiers,
+                                               TapType, LayoutDevicePoint,
-                          ScrollableLayerGuid, uint64_t,
+                                               Modifiers, ScrollableLayerGuid,
+                                               uint64_t,
                                                Maybe<DoubleTapToZoomMetrics>>(
-            "layers::RemoteContentController::HandleTapOnMainThread", this,
+        "layers::RemoteContentController::HandleTapOnParentProcessMainThread",
-            &RemoteContentController::HandleTapOnMainThread, aTapType, aPoint,
+        this, &RemoteContentController::HandleTapOnParentProcessMainThread,
-            aModifiers, aGuid, aInputBlockId, aDoubleTapToZoomMetrics));
+        aTapType, aPoint, aModifiers, aGuid, aInputBlockId,
+        aDoubleTapToZoomMetrics));
 #endif
   }
 }

gfx/layers/ipc/RemoteContentController.h

@@ -98,12 +98,12 @@ class RemoteContentController : public GeckoContentController,
   nsCOMPtr<nsISerialEventTarget> mCompositorThread;
   bool mCanSend;
 
-  void HandleTapOnMainThread(
+  void HandleTapOnParentProcessMainThread(
-      TapType aType, LayoutDevicePoint aPoint, Modifiers aModifiers,
+      TapType aTapType, LayoutDevicePoint aPoint, Modifiers aModifiers,
       ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
       const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics);
-  void HandleTapOnCompositorThread(
+  void HandleTapOnGPUProcessMainThread(
-      TapType aType, LayoutDevicePoint aPoint, Modifiers aModifiers,
+      TapType aTapType, LayoutDevicePoint aPoint, Modifiers aModifiers,
       ScrollableLayerGuid aGuid, uint64_t aInputBlockId,
       const Maybe<DoubleTapToZoomMetrics>& aDoubleTapToZoomMetrics);
   void NotifyPinchGestureOnCompositorThread(