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

ui/app_list/views/progress_bar_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 UI_APP_LIST_VIEWS_PROGRESS_BAR_VIEW_H_
 #define UI_APP_LIST_VIEWS_PROGRESS_BAR_VIEW_H_
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/views/controls/progress_bar.h"
 
 namespace views {
 class Painter;
 }
 
 namespace app_list {
 
 // ProgressBarView implements an image-based progress bar for app launcher.
 class ProgressBarView : public views::ProgressBar {
  public:
   ProgressBarView();
   virtual ~ProgressBarView();
 
   // views::View overrides:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
 
  private:
   scoped_ptr<views::Painter> background_painter_;
   scoped_ptr<views::Painter> bar_painter_;
 
   DISALLOW_COPY_AND_ASSIGN(ProgressBarView);
 };
 
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_VIEWS_PROGRESS_BAR_VIEW_H_