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

ui/views/controls/scrollbar/native_scroll_bar_views.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_VIEWS_H_
 #define UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_VIEWS_H_
 
 #include "base/compiler_specific.h"
 #include "ui/gfx/point.h"
 #include "ui/native_theme/native_theme.h"
@@ skipping 18 matching lines @@
   static const char kViewClassName[];
 
   // Creates new scrollbar, either horizontal or vertical.
   explicit NativeScrollBarViews(NativeScrollBar* native_scroll_bar);
   virtual ~NativeScrollBarViews();
 
  private:
   // View overrides:
   virtual void Layout() OVERRIDE;
   virtual void OnPaint(gfx::Canvas* canvas) OVERRIDE;
-  virtual gfx::Size GetPreferredSize() OVERRIDE;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE;
   virtual const char* GetClassName() const OVERRIDE;
 
   // ScrollBar overrides:
   virtual int GetLayoutSize() const OVERRIDE;
 
   // BaseScrollBar overrides:
   virtual void ScrollToPosition(int position) OVERRIDE;
   virtual int GetScrollIncrement(bool is_page, bool is_positive) OVERRIDE;
 
   // BaseButton::ButtonListener overrides:
@@ skipping 21 matching lines @@
   ui::NativeTheme::ExtraParams params_;
   ui::NativeTheme::Part part_;
   ui::NativeTheme::State state_;
 
   DISALLOW_COPY_AND_ASSIGN(NativeScrollBarViews);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_NATIVE_SCROLL_BAR_VIEWS_H_