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

ui/views/controls/scrollbar/native_scroll_bar.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_SCROLLBAR_NATIVE_SCROLL_BAR_H_
 #define UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_H_
 
 #include <string>
 
 #include "base/compiler_specific.h"
@@ skipping 22 matching lines @@
 
   // Return the system sizes.
   static int GetHorizontalScrollBarHeight(const ui::NativeTheme* theme);
   static int GetVerticalScrollBarWidth(const ui::NativeTheme* theme);
 
  private:
   friend class NativeScrollBarTest;
   FRIEND_TEST_ALL_PREFIXES(NativeScrollBarTest, Scrolling);
 
   // Overridden from View.
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual void Layout() OVERRIDE;
   virtual void ViewHierarchyChanged(
       const ViewHierarchyChangedDetails& details) OVERRIDE;
   virtual const char* GetClassName() const OVERRIDE;
 
   // Overrideen from View for keyboard UI purpose.
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual bool OnMouseWheel(const ui::MouseWheelEvent& e) OVERRIDE;
 
   // Overridden from ui::EventHandler.
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE;
 
   // Overridden from ScrollBar.
   virtual void Update(int viewport_size,
                       int content_size,
                       int current_pos) OVERRIDE;
   virtual int GetPosition() const OVERRIDE;
   virtual int GetLayoutSize() const OVERRIDE;
 
   // init border
   NativeScrollBarWrapper* native_wrapper_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeScrollBar);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_H_