cc: Implement unified BeginFrame on aura

cc/scheduler/scheduler.h

Index: cc/scheduler/scheduler.h
diff --git a/cc/scheduler/scheduler.h b/cc/scheduler/scheduler.h
index 370ac25b6c4bf44a5f50db03c7147bae17192a92..373e2df9024f5a3161d9209bab02af28acfbbb6b 100644
--- a/cc/scheduler/scheduler.h
+++ b/cc/scheduler/scheduler.h
@@ -174,6 +174,8 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn,
 
   void SetChildrenNeedBeginFrames(bool children_need_begin_frames);
 
+  void SetAuthoritativeVSyncInterval(const base::TimeDelta& interval);
+
  protected:
   Scheduler(SchedulerClient* client,
             const SchedulerSettings& scheduler_settings,
@@ -198,6 +200,9 @@ class CC_EXPORT Scheduler : public BeginFrameObserverMixIn,
   scoped_ptr<BeginFrameSource> unthrottled_frame_source_internal_;
 
   VSyncParameterObserver* vsync_observer_;
+  base::TimeDelta authoritative_vsync_interval_;
+  base::TimeTicks last_vsync_timebase_;
+
   bool throttle_frame_production_;
 
   const SchedulerSettings settings_;