Provide a vsync notification to the renderer

cc/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_SURFACE_H_
 #define CC_OUTPUT_SURFACE_H_
 
 #define USE_CC_OUTPUT_SURFACE // TODO(danakj): Remove this.
 
 #include "cc/cc_export.h"
@@ skipping 43 matching lines @@
   virtual SoftwareOutputDevice* SoftwareDevice() const = 0;
 
   // Sends frame data to the parent compositor. This should only be called when
   // capabilities().has_parent_compositor. The implementation may destroy or
   // steal the contents of the CompositorFrame passed in.
   virtual void SendFrameToParentCompositor(CompositorFrame*) = 0;
 
   // 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) {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_SURFACE_H_