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

ash/shell/panel_window.h

 // Copyright (c) 2012 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_SHELL_PANEL_WINDOW_H_
 #define ASH_SHELL_PANEL_WINDOW_H_
 
 #include "base/basictypes.h"
 #include "ui/aura/aura_export.h"
 #include "ui/views/widget/widget.h"
@@ skipping 15 matching lines @@
   views::Widget* CreateWidget();
 
   const std::string& name() { return name_; }
   views::Widget::InitParams& params() { return params_; }
 
   // Creates a panel window and returns the associated widget.
   static views::Widget* CreatePanelWindow(const gfx::Rect& rect);
 
  private:
   // Overridden from views::View:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
 
   // Overridden from views::WidgetDelegate:
   virtual base::string16 GetWindowTitle() const OVERRIDE;
   virtual View* GetContentsView() OVERRIDE;
   virtual bool CanResize() const OVERRIDE;
   virtual bool CanMaximize() const OVERRIDE;
   virtual views::NonClientFrameView* CreateNonClientFrameView(
       views::Widget* widget) OVERRIDE;
 
   std::string name_;
   views::Widget::InitParams params_;
 
   DISALLOW_COPY_AND_ASSIGN(PanelWindow);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_PANEL_WINDOW_H_