views: Make view::Views::GetPreferredSize() const.

ash/frame/caption_buttons/frame_caption_button.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 ASH_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_
 #define ASH_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_
 
 #include "ash/ash_export.h"
 #include "ash/frame/caption_buttons/caption_button_types.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 29 matching lines @@
                  int icon_image_id,
                  int inactive_icon_image_id,
                  int hovered_background_image_id,
                  int pressed_background_image_id);
 
   // Returns true if the button is crossfading to new visuals set in
   // SetImages().
   bool IsAnimatingImageSwap() const;
 
   // views::View overrides:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual const char* GetClassName() const OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
 
   void set_paint_as_active(bool paint_as_active) {
     paint_as_active_ = paint_as_active;
   }
 
   CaptionButtonIcon icon() const {
     return icon_;
   }
@@ skipping 33 matching lines @@
   // Crossfade animation started when the button's images are changed by
   // SetImages().
   scoped_ptr<gfx::SlideAnimation> swap_images_animation_;
 
   DISALLOW_COPY_AND_ASSIGN(FrameCaptionButton);
 };
 
 }  // namespace ash
 
 #endif  // ASH_FRAME_CAPTION_BUTTONS_FRAME_CAPTION_BUTTON_H_