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

ash/system/tray/throbber_view.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 ASH_SYSTEM_TRAY_THROBBER_VIEW_H_
 #define ASH_SYSTEM_TRAY_THROBBER_VIEW_H_
 
 #include "ui/gfx/size.h"
 #include "ui/views/controls/throbber.h"
 #include "ui/views/view.h"
@@ skipping 23 matching lines @@
 class ThrobberView : public views::View {
  public:
   ThrobberView();
   virtual ~ThrobberView();
 
   void Start();
   void Stop();
   void SetTooltipText(const base::string16& tooltip_text);
 
   // Overriden from views::View.
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual bool GetTooltipText(
       const gfx::Point& p, base::string16* tooltip) const OVERRIDE;
 
  private:
   // Schedules animation for starting/stopping throbber.
   void ScheduleAnimation(bool start_throbber);
 
   SystemTrayThrobber* throbber_;
 
   // The current tooltip text.
   base::string16 tooltip_text_;
 
   DISALLOW_COPY_AND_ASSIGN(ThrobberView);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_THROBBER_VIEW_H_