Pass gfx structs by const ref (gfx::Vector2d/F)

ui/aura_extra/image_window_delegate.h

 // Copyright (c) 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 UI_AURA_EXTRA_IMAGE_WINDOW_DELEGATE_H_
 #define UI_AURA_EXTRA_IMAGE_WINDOW_DELEGATE_H_
 
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/aura_extra/aura_extra_export.h"
@@ skipping 10 matching lines @@
 // The delegate destroys itself when the Window is destroyed. This is done in
 // |OnWindowDestroyed()| function which subclasses can override to prevent
 // self-destroying.
 class AURA_EXTRA_EXPORT ImageWindowDelegate : public aura::WindowDelegate {
  public:
   ImageWindowDelegate();
 
   void SetImage(const gfx::Image& image);
 
   void set_background_color(SkColor color) { background_color_ = color; }
-  void set_image_offset(gfx::Vector2d offset) { offset_ = offset; }
+  void set_image_offset(const gfx::Vector2d& offset) { offset_ = offset; }
 
   bool has_image() const { return !image_.IsEmpty(); }
 
  protected:
   ~ImageWindowDelegate() override;
 
   // Overridden from aura::WindowDelegate:
   gfx::Size GetMinimumSize() const override;
   gfx::Size GetMaximumSize() const override;
   void OnBoundsChanged(const gfx::Rect& old_bounds,
@@ skipping 25 matching lines @@
   // the image size is smaller than the window size, then the delegate fills the
   // missing regions with |background_color_| (defult is white).
   bool size_mismatch_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageWindowDelegate);
 };
 
 }  // namespace aura_extra
 
 #endif  // UI_AURA_EXTRA_IMAGE_WINDOW_DELEGATE_H_