cc: Avoid expensive RenderingStats collection.

cc/caching_bitmap_content_layer_updater.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 "caching_bitmap_content_layer_updater.h"
 
 #include "base/logging.h"
 #include "cc/layer_painter.h"
 #include "skia/ext/platform_canvas.h"
 
@@ skipping 16 matching lines @@
   ~CachingBitmapContentLayerUpdater()
 {
 }
 
 void CachingBitmapContentLayerUpdater::prepareToUpdate(
     const gfx::Rect& content_rect,
     const gfx::Size& tile_size,
     float contents_width_scale,
     float contents_height_scale,
     gfx::Rect& resulting_opaque_rect,
-    RenderingStats& stats) {
+    RenderingStats* stats) {
   BitmapContentLayerUpdater::prepareToUpdate(
       content_rect,
       tile_size,
       contents_width_scale,
       contents_height_scale,
       resulting_opaque_rect,
       stats);
 
   const SkBitmap& new_bitmap = m_canvas->getDevice()->accessBitmap(false);
   SkAutoLockPixels lock(new_bitmap);
   DCHECK(new_bitmap.bytesPerPixel() > 0);
   pixels_did_change_ = new_bitmap.config() != cached_bitmap_.config() ||
                        new_bitmap.height() != cached_bitmap_.height() ||
                        new_bitmap.width() != cached_bitmap_.width() ||
                        memcmp(new_bitmap.getPixels(),
                               cached_bitmap_.getPixels(),
                               new_bitmap.getSafeSize());
 
   if (pixels_did_change_)
     new_bitmap.deepCopyTo(&cached_bitmap_, new_bitmap.config());
 }
 
 bool CachingBitmapContentLayerUpdater::pixelsDidChange() const
 {
   return pixels_did_change_;
 }
 
 }  // namespace cc