Tighter sync and faster ACK on SwapBuffers/PostSubBuffers

content/browser/renderer_host/render_widget_host_view_aura.h

Index: content/browser/renderer_host/render_widget_host_view_aura.h
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.h b/content/browser/renderer_host/render_widget_host_view_aura.h
index 0e3fa6effc340213604fa905d37b063198d5935f..efed7dbdaa546fd70c4713241143551f66a5bc60 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.h
+++ b/content/browser/renderer_host/render_widget_host_view_aura.h
@@ -184,6 +184,7 @@ class RenderWidgetHostViewAura
 
   // Overridden from ui::CompositorObserver:
   virtual void OnCompositingStarted(ui::Compositor* compositor) OVERRIDE;
+  virtual void OnCompositingWillEnd(ui::Compositor* compositor) OVERRIDE;
   virtual void OnCompositingEnded(ui::Compositor* compositor) OVERRIDE;
 
   // Overridden from ImageTransportFactoryObserver:
@@ -212,8 +213,10 @@ class RenderWidgetHostViewAura
   // moved to center.
   bool ShouldMoveToCenter();
 
-  // Run the compositing callbacks.
-  void RunCompositingCallbacks();
+  // If compositor == NULL, run all the compositing callbacks. Otherwise,
+  // only run the callbacks that were waiting for
+  // compositor->last_will_end_id().
+  void RunCompositingCallbacks(ui::Compositor* compositor);
 
   // Called when window_ is removed from the window tree.
   void RemovingFromRootWindow();
@@ -266,7 +269,10 @@ class RenderWidgetHostViewAura
   // Current tooltip text.
   string16 tooltip_;
 
-  std::vector< base::Callback<void(void)> > on_compositing_ended_callbacks_;
+  // Callback and the number of the will end composite that it should run on.
+  typedef std::pair<base::Callback<void(void)>, int>
+      CallbackAndCompositeNumber;
+  std::vector<CallbackAndCompositeNumber> on_compositing_will_end_callbacks_;
 
   std::map<uint64, scoped_refptr<ImageTransportClient> >
       image_transport_clients_;