[cc] Add and use BeginFrameAck for DidFinishFrame.

cc/scheduler/scheduler_state_machine.h

Index: cc/scheduler/scheduler_state_machine.h
diff --git a/cc/scheduler/scheduler_state_machine.h b/cc/scheduler/scheduler_state_machine.h
index b04bd9b85a35ee5d2d90959f25a31b252919ab88..3272588d56894ee6b27ef4fd2977109052bbba27 100644
--- a/cc/scheduler/scheduler_state_machine.h
+++ b/cc/scheduler/scheduler_state_machine.h
@@ -269,6 +269,8 @@ class CC_EXPORT SchedulerStateMachine {
   void SetVideoNeedsBeginFrames(bool video_needs_begin_frames);
   bool video_needs_begin_frames() const { return video_needs_begin_frames_; }
 
+  bool did_submit_in_last_frame() const { return did_submit_in_last_frame_; }
+
  protected:
   bool BeginFrameRequiredForAction() const;
   bool BeginFrameNeededForVideo() const;