Use overlay scrollbars for the cros system menu.

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 "base/macros.h"
 #include "ui/views/animation/scroll_animator.h"
@@ skipping 50 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:
-  gfx::Size GetPreferredSize() const override = 0;
-  void Layout() override = 0;
   bool OnMousePressed(const ui::MouseEvent& event) override;
   void OnMouseReleased(const ui::MouseEvent& event) override;
   void OnMouseCaptureLost() override;
   void OnMouseEntered(const ui::MouseEvent& event) override;
   void OnMouseExited(const ui::MouseEvent& event) override;
   bool OnKeyPressed(const ui::KeyEvent& event) override;
   bool OnMouseWheel(const ui::MouseWheelEvent& event) override;
 
   // ui::EventHandler overrides:
   void OnGestureEvent(ui::GestureEvent* event) override;
@@ skipping 12 matching lines @@
   void ShowContextMenuForView(View* source,
                               const gfx::Point& point,
                               ui::MenuSourceType source_type) override;
 
   // Menu::Delegate overrides:
   base::string16 GetLabel(int id) const override;
   bool IsCommandEnabled(int id) const override;
   void ExecuteCommand(int id) override;
 
  protected:
-  // View overrides:
-  void OnPaint(gfx::Canvas* canvas) override = 0;
-
   BaseScrollBarThumb* GetThumb() const;
   CustomButton::ButtonState GetThumbTrackState() const;
 
   // Wrapper functions that calls the controller. We need this since native
   // scrollbars wrap around a different scrollbar. When calling the controller
   // we need to pass in the appropriate scrollbar. For normal scrollbars it's
   // the |this| scrollbar, for native scrollbars it's the native scrollbar used
   // to create this.
   virtual void ScrollToPosition(int position);
   virtual int GetScrollIncrement(bool is_page, bool is_positive);
@@ skipping 72 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_