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

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 12 matching lines @@
   // Allows updaters to store per-resource update properties.
   class CC_EXPORT Resource {
    public:
     virtual ~Resource();
 
     PrioritizedResource* texture() { return texture_.get(); }
     // TODO(reveman): partial_update should be a property of this class
     // instead of an argument passed to Update().
     virtual void Update(ResourceUpdateQueue* queue,
                         const gfx::Rect& source_rect,
-                        gfx::Vector2d dest_offset,
+                        const gfx::Vector2d& dest_offset,
                         bool partial_update) = 0;
    protected:
     explicit Resource(scoped_ptr<PrioritizedResource> texture);
 
    private:
     scoped_ptr<PrioritizedResource> texture_;
 
     DISALLOW_COPY_AND_ASSIGN(Resource);
   };
 
@@ skipping 20 matching lines @@
 
  private:
   friend class base::RefCounted<LayerUpdater>;
 
   DISALLOW_COPY_AND_ASSIGN(LayerUpdater);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_LAYER_UPDATER_H_