Aggregate damage rects in surface aggregator

cc/surfaces/surface.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_H_
 #define CC_SURFACES_SURFACE_H_
 
 #include "base/callback.h"
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
@@ skipping 14 matching lines @@
   ~Surface();
 
   const gfx::Size& size() const { return size_; }
   SurfaceId surface_id() const { return surface_id_; }
 
   void QueueFrame(scoped_ptr<CompositorFrame> frame,
                   const base::Closure& draw_callback);
   // Returns the most recent frame that is eligible to be rendered.
   const CompositorFrame* GetEligibleFrame();
 
+  // Returns a number that increments by 1 every time a new frame is enqueued.
+  int frame_index() const { return frame_index_; }
+
   void RunDrawCallbacks();
 
   SurfaceFactory* factory() { return factory_; }
 
  private:
   SurfaceId surface_id_;
   gfx::Size size_;
   SurfaceFactory* factory_;
   // TODO(jamesr): Support multiple frames in flight.
   scoped_ptr<CompositorFrame> current_frame_;
+  int frame_index_;
 
   base::Closure draw_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Surface);
 };
 
 }  // namespace cc
 
 #endif  // CC_SURFACES_SURFACE_H_