[cc] CompositorFrameSinkSupport: Defer BeginFrameAck of pending frames.

cc/surfaces/surface_factory_client.h

Index: cc/surfaces/surface_factory_client.h
diff --git a/cc/surfaces/surface_factory_client.h b/cc/surfaces/surface_factory_client.h
index ea32344afcd0922ead3f79f948553c264b8b636e..b19a746dc27d86dc80b611fdd497bf7ef0550877 100644
--- a/cc/surfaces/surface_factory_client.h
+++ b/cc/surfaces/surface_factory_client.h
@@ -29,6 +29,10 @@ class CC_SURFACES_EXPORT SurfaceFactoryClient {
   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;
 };