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

ash/system/tray/fixed_sized_image_view.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_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_
 #define ASH_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "ui/views/controls/image_view.h"
 
 namespace ash {
 
 // An image view with a specified width and height (kTrayPopupDetailsIconWidth).
 // If the specified width or height is zero, then the image size is used for
 // that dimension.
 class FixedSizedImageView : public views::ImageView {
  public:
   FixedSizedImageView(int width, int height);
   virtual ~FixedSizedImageView();
 
  private:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
 
   int width_;
   int height_;
 
   DISALLOW_COPY_AND_ASSIGN(FixedSizedImageView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_FIXED_SIZED_IMAGE_VIEW_H_