Bug 930939 - Add a function to encapsulate running things on the APZ controller thread. r=botond

gfx/layers/apz/util/APZThreadUtils.cpp

@@ -49,5 +49,23 @@ APZThreadUtils::AssertOnCompositorThread()
   }
 }
 
+/*static*/ void
+APZThreadUtils::RunOnControllerThread(Task* aTask)
+{
+#ifdef MOZ_WIDGET_GONK
+  // On B2G the controller thread is the compositor thread, and this function
+  // is always called from the libui thread or the main thread.
+  MessageLoop* loop = CompositorParent::CompositorLoop();
+  MOZ_ASSERT(MessageLoop::current() != loop);
+  loop->PostTask(FROM_HERE, aTask);
+#else
+  // On non-B2G platforms this is only ever called from the controller thread
+  // itself.
+  AssertOnControllerThread();
+  aTask->Run();
+  delete aTask;
+#endif
+}
+
 } // namespace layers
 } // namespace mozilla

gfx/layers/apz/util/APZThreadUtils.h

@@ -6,6 +6,8 @@
 #ifndef mozilla_layers_APZThreadUtils_h
 #define mozilla_layers_APZThreadUtils_h
 
+class Task;
+
 namespace mozilla {
 namespace layers {
 
@@ -33,6 +35,13 @@ public:
    * This does nothing if thread assertions are disabled.
    */
   static void AssertOnCompositorThread();
+
+  /**
+   * Run the given task on the APZ "controller thread" for this platform. If
+   * this function is called from the controller thread itself then the task is
+   * run immediately without getting queued.
+   */
+  static void RunOnControllerThread(Task* aTask);
 };
 
 } // namespace layers

layout/ipc/RenderFrameParent.cpp

@@ -16,6 +16,7 @@
 #include "mozilla/dom/ContentChild.h"
 #include "mozilla/dom/TabParent.h"
 #include "mozilla/layers/APZCTreeManager.h"
+#include "mozilla/layers/APZThreadUtils.h"
 #include "mozilla/layers/CompositorParent.h"
 #include "mozilla/layers/LayerTransactionParent.h"
 #include "nsContentUtils.h"
@@ -531,7 +532,9 @@ RenderFrameParent::ContentReceivedInputBlock(const ScrollableLayerGuid& aGuid,
     return;
   }
   if (GetApzcTreeManager()) {
-    GetApzcTreeManager()->ContentReceivedInputBlock(aInputBlockId, aPreventDefault);
+    APZThreadUtils::RunOnControllerThread(NewRunnableMethod(
+        GetApzcTreeManager(), &APZCTreeManager::ContentReceivedInputBlock,
+        aInputBlockId, aPreventDefault));
   }
 }
 
@@ -547,7 +550,12 @@ RenderFrameParent::SetTargetAPZC(uint64_t aInputBlockId,
     }
   }
   if (GetApzcTreeManager()) {
-    GetApzcTreeManager()->SetTargetAPZC(aInputBlockId, aTargets);
+    // need a local var to disambiguate between the SetTargetAPZC overloads.
+    void (APZCTreeManager::*setTargetApzcFunc)(uint64_t, const nsTArray<ScrollableLayerGuid>&)
+        = &APZCTreeManager::SetTargetAPZC;
+    APZThreadUtils::RunOnControllerThread(NewRunnableMethod(
+        GetApzcTreeManager(), setTargetApzcFunc,
+        aInputBlockId, aTargets));
   }
 }