[cc] CompositorFrameSinkSupport: Defer BeginFrameAck of pending frames.

cc/surfaces/surface_factory_client.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CC_SURFACES_SURFACE_FACTORY_CLIENT_H_
 #define CC_SURFACES_SURFACE_FACTORY_CLIENT_H_
 
 #include "cc/resources/returned_resource.h"
 #include "cc/surfaces/local_surface_id.h"
 #include "cc/surfaces/surfaces_export.h"
@@ skipping 11 matching lines @@
   virtual void ReferencedSurfacesChanged(
       const LocalSurfaceId& local_surface_id,
       const std::vector<SurfaceId>* active_referenced_surfaces,
       const std::vector<SurfaceId>* pending_referenced_surfaces) {}
 
   virtual void ReturnResources(const ReturnedResourceArray& resources) = 0;
 
   virtual void WillDrawSurface(const LocalSurfaceId& local_surface_id,
                                const gfx::Rect& damage_rect) {}
 
+  virtual void PendingFrameActivated(const LocalSurfaceId& local_surface_id) {}
+
+  virtual void SurfaceDiscarded(const LocalSurfaceId& local_surface_id) {}
+
   // This allows the SurfaceFactory to pass a BeginFrameSource to use.
   virtual void SetBeginFrameSource(BeginFrameSource* begin_frame_source) = 0;
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_FACTORY_CLIENT_H_