[#6]Pass gfx structs by const ref (gfx::Vector2d)

cc/resources/bitmap_content_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_BITMAP_CONTENT_LAYER_UPDATER_H_
 #define CC_RESOURCES_BITMAP_CONTENT_LAYER_UPDATER_H_
 
 #include "cc/base/cc_export.h"
 #include "cc/resources/content_layer_updater.h"
 #include "skia/ext/refptr.h"
@@ skipping 13 matching lines @@
 class CC_EXPORT BitmapContentLayerUpdater : public ContentLayerUpdater {
  public:
   class Resource : public LayerUpdater::Resource {
    public:
     Resource(BitmapContentLayerUpdater* updater,
              scoped_ptr<PrioritizedResource> resource);
     virtual ~Resource();
 
     virtual void Update(ResourceUpdateQueue* queue,
                         const gfx::Rect& source_rect,
-                        gfx::Vector2d dest_offset,
+                        const gfx::Vector2d& dest_offset,
                         bool partial_update) OVERRIDE;
 
    private:
     BitmapContentLayerUpdater* updater_;
 
     DISALLOW_COPY_AND_ASSIGN(Resource);
   };
 
   static scoped_refptr<BitmapContentLayerUpdater> Create(
       scoped_ptr<LayerPainter> painter,
       RenderingStatsInstrumentation* stats_instrumenation,
       int layer_id);
 
   virtual scoped_ptr<LayerUpdater::Resource> CreateResource(
       PrioritizedResourceManager* manager) OVERRIDE;
   virtual void PrepareToUpdate(const gfx::Rect& content_rect,
                                const gfx::Size& tile_size,
                                float contents_width_scale,
                                float contents_height_scale,
                                gfx::Rect* resulting_opaque_rect) OVERRIDE;
   void UpdateTexture(ResourceUpdateQueue* queue,
                      PrioritizedResource* resource,
                      const gfx::Rect& source_rect,
-                     gfx::Vector2d dest_offset,
+                     const gfx::Vector2d& dest_offset,
                      bool partial_update);
   virtual void SetOpaque(bool opaque) OVERRIDE;
   virtual void ReduceMemoryUsage() OVERRIDE;
 
  protected:
   BitmapContentLayerUpdater(
       scoped_ptr<LayerPainter> painter,
       RenderingStatsInstrumentation* stats_instrumenation,
       int layer_id);
   virtual ~BitmapContentLayerUpdater();
 
   SkBitmap bitmap_backing_;
   skia::RefPtr<SkCanvas> canvas_;
   gfx::Size canvas_size_;
   bool opaque_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BitmapContentLayerUpdater);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_BITMAP_CONTENT_LAYER_UPDATER_H_