Add SurfaceWillDraw notification

cc/surfaces/surface_manager.h

 // Copyright 2014 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_SURFACE_MANAGER_H_
 #define CC_SURFACES_SURFACE_MANAGER_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 56 matching lines @@
 
   void RequestSurfaceResolution(Surface* pending_surface);
 
   std::unique_ptr<Surface> CreateSurface(
       base::WeakPtr<CompositorFrameSinkSupport> compositor_frame_sink_support,
       const SurfaceInfo& surface_info);
 
   // Destroy the Surface once a set of sequence numbers has been satisfied.
   void DestroySurface(std::unique_ptr<Surface> surface);
 
+  // Called when a surface has been added to the Display Frame and will

[danakj, 2017/06/14 18:53:12]

Display Frame is written like it is a type, but I don't think it is. You're
referring to the aggregated CompositorFrame in the Display, I believe.

[gklassen, 2017/06/14 19:29:11]

Good call.  Your suggestion makes the description clearer.  Thank you. 
 
Done.

+  // invoke observers with the OnSurfaceWillDraw notification.
+  void SurfaceWillDraw(const SurfaceId& surface_id);
+
   Surface* GetSurfaceForId(const SurfaceId& surface_id);
 
   void AddObserver(SurfaceObserver* obs) { observer_list_.AddObserver(obs); }
 
   void RemoveObserver(SurfaceObserver* obs) {
     observer_list_.RemoveObserver(obs);
   }
 
   // Called when a Surface is modified, e.g. when a CompositorFrame is
   // activated, its producer confirms that no CompositorFrame will be submitted
@@ skipping 239 matching lines @@
   SurfaceDependencyTracker* dependency_tracker_ = nullptr;
 
   base::WeakPtrFactory<SurfaceManager> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceManager);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_MANAGER_H_