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

cc/resources/resource_update.cc

 // 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.
 
 #include "cc/resources/resource_update.h"
 
 #include "base/logging.h"
 
 namespace cc {
 
 ResourceUpdate ResourceUpdate::Create(PrioritizedResource* resource,
                                       const SkBitmap* bitmap,
                                       const gfx::Rect& content_rect,
                                       const gfx::Rect& source_rect,
-                                      gfx::Vector2d dest_offset) {
+                                      const gfx::Vector2d& dest_offset) {
   CHECK(content_rect.Contains(source_rect));
   ResourceUpdate update;
   update.texture = resource;
   update.bitmap = bitmap;
   update.content_rect = content_rect;
   update.source_rect = source_rect;
   update.dest_offset = dest_offset;
   return update;
 }
 
 ResourceUpdate::ResourceUpdate()
     : texture(NULL),
       bitmap(NULL) {}
 
 ResourceUpdate::~ResourceUpdate() {}
 
 }  // namespace cc