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

cc/test/solid_color_content_layer_client.h

 // Copyright 2013 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_TEST_SOLID_COLOR_CONTENT_LAYER_CLIENT_H_
 #define CC_TEST_SOLID_COLOR_CONTENT_LAYER_CLIENT_H_
 
 #include "base/compiler_specific.h"
 #include "cc/layers/content_layer_client.h"
 #include "third_party/skia/include/core/SkColor.h"
 
 namespace cc {
 
 class SolidColorContentLayerClient : public ContentLayerClient {
  public:
   explicit SolidColorContentLayerClient(SkColor color) : color_(color) {}
 
   // ContentLayerClient implementation.
   virtual void DidChangeLayerCanUseLCDText() OVERRIDE {}
   virtual void PaintContents(SkCanvas* canvas,
-                             gfx::Rect rect,
+                             const gfx::Rect& rect,
                              gfx::RectF* opaque_rect) OVERRIDE;
 
  private:
   SkColor color_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_SOLID_COLOR_CONTENT_LAYER_CLIENT_H_