[cc] Mailbox Output Surface Support

content/renderer/gpu/compositor_output_surface.h

Index: content/renderer/gpu/compositor_output_surface.h
diff --git a/content/renderer/gpu/compositor_output_surface.h b/content/renderer/gpu/compositor_output_surface.h
index fa8e4c6dd8ae08439316410fac41eabf8a69fad7..896325c462b84faaf03d62c4867a6e3e89f14d6d 100644
--- a/content/renderer/gpu/compositor_output_surface.h
+++ b/content/renderer/gpu/compositor_output_surface.h
@@ -23,6 +23,10 @@ class ForwardingMessageFilter;
 class Message;
 }
 
+namespace cc {
+class CompositorFrameAck;
+}
+
 namespace content {
 
 // This class can be created only on the main thread, but then becomes pinned
@@ -47,6 +51,9 @@ class CompositorOutputSurface
   // int CompositorThread after it is fully refactored (http://crbug/170828)
   virtual void UpdateSmoothnessTakesPriority(bool prefer_smoothness) OVERRIDE;
 
+ protected:
+  virtual void OnSwapAck(const cc::CompositorFrameAck& ack);
+
  private:
   class CompositorOutputSurfaceProxy :
       public base::RefCountedThreadSafe<CompositorOutputSurfaceProxy> {