It is time.

ui/views/controls/scrollbar/overlay_scroll_bar.h

-// Copyright 2013 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_OVERLAY_SCROLL_BAR_H_
-#define UI_VIEWS_CONTROLS_SCROLLBAR_OVERLAY_SCROLL_BAR_H_
-
-#include "ui/gfx/animation/slide_animation.h"
-#include "ui/views/controls/scrollbar/base_scroll_bar.h"
-
-namespace views {
-
-// The transparent scrollbar which overlays its contents.
-class VIEWS_EXPORT OverlayScrollBar : public BaseScrollBar {
- public:
-  explicit OverlayScrollBar(bool horizontal);
-  virtual ~OverlayScrollBar();
-
- protected:
-  // BaseScrollBar overrides:
-  virtual gfx::Rect GetTrackBounds() const override;
-  virtual void OnGestureEvent(ui::GestureEvent* event) override;
-
-  // ScrollBar overrides:
-  virtual int GetLayoutSize() const override;
-  virtual int GetContentOverlapSize() const override;
-  virtual void OnMouseEnteredScrollView(const ui::MouseEvent& event) override;
-  virtual void OnMouseExitedScrollView(const ui::MouseEvent& event) override;
-
-  // View overrides:
-  virtual gfx::Size GetPreferredSize() const override;
-  virtual void Layout() override;
-  virtual void OnPaint(gfx::Canvas* canvas) override;
-
- private:
-  gfx::SlideAnimation animation_;
-  DISALLOW_COPY_AND_ASSIGN(OverlayScrollBar);
-};
-
-}  // namespace views
-
-#endif  // UI_VIEWS_CONTROLS_SCROLLBAR_OVERLAY_SCROLL_BAR_H_