[#7] Pass gfx structs by const ref (gfx::Size)

cc/resources/layer_updater.h

 // Copyright 2011 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_LAYER_UPDATER_H_
 #define CC_RESOURCES_LAYER_UPDATER_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "cc/base/cc_export.h"
@@ skipping 31 matching lines @@
   };
 
   LayerUpdater() {}
 
   virtual scoped_ptr<Resource> CreateResource(
       PrioritizedResourceManager* manager) = 0;
   // The |resulting_opaque_rect| gives back a region of the layer that was
   // painted opaque. If the layer is marked opaque in the updater, then this
   // region should be ignored in preference for the entire layer's area.
   virtual void PrepareToUpdate(const gfx::Rect& content_rect,
-                               gfx::Size tile_size,
+                               const gfx::Size& tile_size,
                                float contents_width_scale,
                                float contents_height_scale,
                                gfx::Rect* resulting_opaque_rect) {}
   virtual void ReduceMemoryUsage() {}
 
   // Set true by the layer when it is known that the entire output is going to
   // be opaque.
   virtual void SetOpaque(bool opaque) {}
 
  protected:
   virtual ~LayerUpdater() {}
 
  private:
   friend class base::RefCounted<LayerUpdater>;
 
   DISALLOW_COPY_AND_ASSIGN(LayerUpdater);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_LAYER_UPDATER_H_