cc: Avoid expensive RenderingStats collection.

cc/test/fake_scrollbar_layer.cc

 // 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.
 
 #include "cc/test/fake_scrollbar_layer.h"
 
 #include "cc/resource_update_queue.h"
 #include "cc/test/fake_scrollbar_theme_painter.h"
 #include "cc/test/fake_web_scrollbar.h"
 #include "cc/test/fake_web_scrollbar_theme_geometry.h"
@@ skipping 15 matching lines @@
   setAnchorPoint(gfx::PointF(0, 0));
   setBounds(gfx::Size(1, 1));
   setIsDrawable(true);
 }
 
 FakeScrollbarLayer::~FakeScrollbarLayer() {}
 
 void FakeScrollbarLayer::update(
     ResourceUpdateQueue& queue,
     const OcclusionTracker* occlusion,
-    RenderingStats& stats) {
+    RenderingStats* stats) {
   size_t full = queue.fullUploadSize();
   size_t partial = queue.partialUploadSize();
   ScrollbarLayer::update(queue, occlusion, stats);
   update_count_++;
   last_update_full_upload_size_ = queue.fullUploadSize() - full;
   last_update_partial_upload_size_ = queue.partialUploadSize() - partial;
 }
 
 }  // namespace cc