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

ui/views/controls/slider.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 UI_VIEWS_CONTROLS_SLIDER_H_
 #define UI_VIEWS_CONTROLS_SLIDER_H_
 
 #include "ui/gfx/animation/animation_delegate.h"
 #include "ui/views/view.h"
 #include "ui/views/views_export.h"
@@ skipping 64 matching lines @@
   // position of the mouse cursor (or the touch point) on the button to
   // accurately move the button using the MoveButtonTo() method.
   void PrepareForMove(const gfx::Point& point);
 
   // Moves the button to the specified point and updates the value accordingly.
   void MoveButtonTo(const gfx::Point& point);
 
   void OnPaintFocus(gfx::Canvas* canvas);
 
   // views::View overrides:
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
   virtual bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE;
   virtual bool OnMouseDragged(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual void GetAccessibleState(ui::AXViewState* state) OVERRIDE;
   virtual void OnFocus() OVERRIDE;
   virtual void OnBlur() OVERRIDE;
 
   // ui::EventHandler overrides:
@@ skipping 24 matching lines @@
   const gfx::ImageSkia* thumb_;
   const gfx::ImageSkia* images_[4];
   int bar_height_;
 
   DISALLOW_COPY_AND_ASSIGN(Slider);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SLIDER_H_