Add SurfaceWillDraw notification

cc/surfaces/display_scheduler.h

 // Copyright 2015 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_SURFACES_DISPLAY_SCHEDULER_H_
 #define CC_SURFACES_DISPLAY_SCHEDULER_H_
 
 #include <memory>
 
 #include "base/cancelable_callback.h"
@@ skipping 52 matching lines @@
   void OnBeginFrameSourcePausedChanged(bool paused) override;
 
   // SurfaceObserver implementation.
   void OnSurfaceCreated(const SurfaceInfo& surface_info) override;
   void OnSurfaceDestroyed(const SurfaceId& surface_id) override;
   bool OnSurfaceDamaged(const SurfaceId& surface_id,
                         const BeginFrameAck& ack) override;
   void OnSurfaceDiscarded(const SurfaceId& surface_id) override;
   void OnSurfaceDamageExpected(const SurfaceId& surface_id,
                                const BeginFrameArgs& args) override;
+  void OnSurfaceWillDraw(const SurfaceId& surface_id) override;
 
  protected:
   base::TimeTicks DesiredBeginFrameDeadlineTime();
   virtual void ScheduleBeginFrameDeadline();
   bool AttemptDrawAndSwap();
   void OnBeginFrameDeadline();
   bool DrawAndSwap();
   void StartObservingBeginFrames();
   void StopObservingBeginFrames();
   bool ShouldDraw();
@@ skipping 38 matching lines @@
 
   base::WeakPtrFactory<DisplayScheduler> weak_ptr_factory_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(DisplayScheduler);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_DISPLAY_SCHEDULER_H_