[cc] Add and use BeginFrameAck for DidFinishFrame.

cc/surfaces/display_scheduler.h

Index: cc/surfaces/display_scheduler.h
diff --git a/cc/surfaces/display_scheduler.h b/cc/surfaces/display_scheduler.h
index cda88e5819bc948ff783192659a8b0b5e1f09b15..83d1300039351fac242795d8842009331cc62fda 100644
--- a/cc/surfaces/display_scheduler.h
+++ b/cc/surfaces/display_scheduler.h
@@ -55,12 +55,13 @@ class CC_SURFACES_EXPORT DisplayScheduler : public BeginFrameObserverBase {
  protected:
   base::TimeTicks DesiredBeginFrameDeadlineTime();
   virtual void ScheduleBeginFrameDeadline();
-  void AttemptDrawAndSwap();
+  bool AttemptDrawAndSwap();
   void OnBeginFrameDeadline();
-  void DrawAndSwap();
+  bool DrawAndSwap();
   void StartObservingBeginFrames();
   void StopObservingBeginFrames();
   bool ShouldDraw();
+  void DidFinishFrame(bool did_draw);
 
   DisplaySchedulerClient* client_;
   BeginFrameSource* begin_frame_source_;