cc: Don't pass simple well-defined classes by reference.

cc/resources/picture_layer_tiling.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_RESOURCES_PICTURE_LAYER_TILING_H_
 #define CC_RESOURCES_PICTURE_LAYER_TILING_H_
 
 #include <utility>
 #include <vector>
 
@@ skipping 105 matching lines @@
     int tile_i_;
     int tile_j_;
     int left_;
     int top_;
     int right_;
     int bottom_;
 
     friend class PictureLayerTiling;
   };
 
-  Region OpaqueRegionInContentRect(const gfx::Rect&) const;
+  Region OpaqueRegionInContentRect(gfx::Rect content_rect) const;
 
   void Reset() { return tiles_.clear(); }
 
   void UpdateTilePriorities(
       WhichTree tree,
       gfx::Size device_viewport,
       const gfx::RectF& viewport_in_layer_space,
       const gfx::RectF& visible_layer_rect,
       gfx::Size last_layer_bounds,
       gfx::Size current_layer_bounds,
@@ skipping 35 matching lines @@
 
   friend class CoverageIterator;
 
  private:
   DISALLOW_ASSIGN(PictureLayerTiling);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_PICTURE_LAYER_TILING_H_