cc: Avoid expensive RenderingStats collection.

cc/test/fake_scrollbar_layer.h

 // Copyright 2012 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_TEST_FAKE_SCROLLBAR_LAYER_H_
 #define CC_TEST_FAKE_SCROLLBAR_LAYER_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "cc/scrollbar_layer.h"
 
@@ skipping 12 matching lines @@
   size_t last_update_full_upload_size() const {
     return last_update_full_upload_size_;
   }
   size_t last_update_partial_upload_size() const {
     return last_update_partial_upload_size_;
   }
 
   virtual void update(
       ResourceUpdateQueue& queue,
       const OcclusionTracker* occlusion,
-      RenderingStats& stats) OVERRIDE;
+      RenderingStats* stats) OVERRIDE;
 
 private:
   FakeScrollbarLayer(
       bool paint_during_update, bool has_thumb, int scrolling_layer_id);
   virtual ~FakeScrollbarLayer();
 
   int update_count_;
   size_t last_update_full_upload_size_;
   size_t last_update_partial_upload_size_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_SCROLLBAR_LAYER_H_