cc: Hook vsync time source to output surface

cc/output/output_surface.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_H_
 #define CC_OUTPUT_OUTPUT_SURFACE_H_
 
 #define USE_CC_OUTPUT_SURFACE // TODO(danakj): Remove this.
 
 #include "base/basictypes.h"
@@ skipping 73 matching lines @@
 
   virtual void BindFramebuffer();
 
   virtual void PostSubBuffer(gfx::Rect rect);
   virtual void SwapBuffers();
 
   // Notifies frame-rate smoothness preference. If true, all non-critical
   // processing should be stopped, or lowered in priority.
   virtual void UpdateSmoothnessTakesPriority(bool prefer_smoothness) {}
 
+  // Requests a vsync notification from the output surface. The notification
+  // will be delivered by calling OutputSurfaceClient::DidVSync for all future
+  // vsync events until the callback is disabled.
+  virtual void EnableVSyncNotification(bool enable_vsync) {}
+
  protected:
   OutputSurfaceClient* client_;
   struct cc::OutputSurface::Capabilities capabilities_;
   scoped_ptr<WebKit::WebGraphicsContext3D> context3d_;
   scoped_ptr<cc::SoftwareOutputDevice> software_device_;
   bool has_gl_discard_backbuffer_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OutputSurface);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OUTPUT_SURFACE_H_