cc: Hook vsync time source to output surface

cc/output/output_surface_client.h

 // Copyright 2012 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_OUTPUT_OUTPUT_SURFACE_CLIENT_H_
 #define CC_OUTPUT_OUTPUT_SURFACE_CLIENT_H_
 
 #include "base/time.h"
 #include "cc/base/cc_export.h"
 
 namespace cc {
 
 class CompositorFrameAck;
 
 class CC_EXPORT OutputSurfaceClient {
  public:
   virtual void OnVSyncParametersChanged(base::TimeTicks timebase,
                                         base::TimeDelta interval) = 0;
+  virtual void DidVSync(base::TimeTicks frame_time) = 0;
   virtual void OnSendFrameToParentCompositorAck(const CompositorFrameAck&) = 0;
 
  protected:
   virtual ~OutputSurfaceClient() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OUTPUT_SURFACE_CLIENT_H_