Bug 1124452 - Ensure the widget continues to be destroyed on the main thread. r=BenWa

gfx/layers/apz/public/GeckoContentController.h

@@ -157,6 +157,7 @@ public:
                                     int aArg = 0) {}
 
   GeckoContentController() {}
+  virtual void Destroy() {}
 
 protected:
   // Protected destructor, to discourage deletion outside of Release():

gfx/layers/apz/util/ChromeProcessController.cpp

@@ -83,3 +83,17 @@ ChromeProcessController::AcknowledgeScrollUpdate(const FrameMetrics::ViewID& aSc
 {
   APZCCallbackHelper::AcknowledgeScrollUpdate(aScrollId, aScrollGeneration);
 }
+
+void
+ChromeProcessController::Destroy()
+{
+  if (MessageLoop::current() != mUILoop) {
+    mUILoop->PostTask(
+      FROM_HERE,
+      NewRunnableMethod(this, &ChromeProcessController::Destroy));
+    return;
+  }
+
+  MOZ_ASSERT(MessageLoop::current() == mUILoop);
+  mWidget = nullptr;
+}

gfx/layers/apz/util/ChromeProcessController.h

@@ -27,6 +27,7 @@ class ChromeProcessController : public mozilla::layers::GeckoContentController
 
 public:
   explicit ChromeProcessController(nsIWidget* aWidget);
+  virtual void Destroy() MOZ_OVERRIDE;
 
   // GeckoContentController interface
   virtual void RequestContentRepaint(const FrameMetrics& aFrameMetrics) MOZ_OVERRIDE;

gfx/layers/ipc/CompositorParent.cpp

@@ -88,6 +88,13 @@ CompositorParent::LayerTreeState::LayerTreeState()
 {
 }
 
+CompositorParent::LayerTreeState::~LayerTreeState()
+{
+  if (mController) {
+    mController->Destroy();
+  }
+}
+
 typedef map<uint64_t, CompositorParent::LayerTreeState> LayerTreeMap;
 static LayerTreeMap sIndirectLayerTrees;
 static StaticAutoPtr<mozilla::Monitor> sIndirectLayerTreesLock;

gfx/layers/ipc/CompositorParent.h

@@ -291,6 +291,7 @@ public:
 
   struct LayerTreeState {
     LayerTreeState();
+    ~LayerTreeState();
     nsRefPtr<Layer> mRoot;
     nsRefPtr<GeckoContentController> mController;
     CompositorParent* mParent;