[#2] Pass gfx structs by const ref (gfx::Rect, gfx::RectF)

cc/layers/picture_image_layer.h

 // Copyright 2010 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_LAYERS_PICTURE_IMAGE_LAYER_H_
 #define CC_LAYERS_PICTURE_IMAGE_LAYER_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/layers/content_layer_client.h"
 #include "cc/layers/picture_layer.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/size.h"
 
 namespace cc {
 
 class CC_EXPORT PictureImageLayer : public PictureLayer, ContentLayerClient {
  public:
   static scoped_refptr<PictureImageLayer> Create();
 
   void SetBitmap(const SkBitmap& image);
 
   // Layer implementation.
   virtual scoped_ptr<LayerImpl> CreateLayerImpl(
       LayerTreeImpl* tree_impl) OVERRIDE;
   virtual bool DrawsContent() const OVERRIDE;
 
   // ContentLayerClient implementation.
   virtual void PaintContents(
       SkCanvas* canvas,
-      gfx::Rect clip,
+      const gfx::Rect& clip,
       gfx::RectF* opaque) OVERRIDE;
   virtual void DidChangeLayerCanUseLCDText() OVERRIDE {}
 
  private:
   PictureImageLayer();
   virtual ~PictureImageLayer();
 
   SkBitmap bitmap_;
 
   DISALLOW_COPY_AND_ASSIGN(PictureImageLayer);
 };
 
 }  // namespace cc
 
 #endif  // CC_LAYERS_PICTURE_IMAGE_LAYER_H_