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

ui/views/controls/scrollbar/base_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_BASE_SCROLL_BAR_H_
 #define UI_VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_H_
 
 #include "base/gtest_prod_util.h"
 #include "ui/views/animation/scroll_animator.h"
 #include "ui/views/context_menu_controller.h"
@@ skipping 46 matching lines @@
 
   // Scroll the contents by the specified offset (contents coordinates).
   bool ScrollByContentsOffset(int contents_offset);
 
   // Called when the thumb state has been changed from |old_state| to
   // |new_state|.
   void OnThumbStateChanged(CustomButton::ButtonState old_state,
                            CustomButton::ButtonState new_state);
 
   // View overrides:
-  virtual gfx::Size GetPreferredSize() OVERRIDE = 0;
+  virtual gfx::Size GetPreferredSize() const OVERRIDE = 0;
   virtual void Layout() OVERRIDE = 0;
   virtual bool OnMousePressed(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseReleased(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseCaptureLost() OVERRIDE;
   virtual void OnMouseEntered(const ui::MouseEvent& event) OVERRIDE;
   virtual void OnMouseExited(const ui::MouseEvent& event) OVERRIDE;
   virtual bool OnKeyPressed(const ui::KeyEvent& event) OVERRIDE;
   virtual bool OnMouseWheel(const ui::MouseWheelEvent& event) OVERRIDE;
 
   // ui::EventHandler overrides:
@@ skipping 105 matching lines @@
   // TODO(tdresser): This should be removed when raw pixel scrolling for views
   // is enabled. See crbug.com/329354.
   gfx::Vector2dF roundoff_error_;
 
   DISALLOW_COPY_AND_ASSIGN(BaseScrollBar);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_CONTROLS_SCROLLBAR_BASE_SCROLL_BAR_H_