Implement Sebastien's overlay scrollbars for native UI (Views).

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 44 matching lines @@
 
   // Scroll the contents to the appropriate position given the supplied
   // position of the thumb (thumb track coordinates). If |scroll_to_middle| is
   // true, then the conversion assumes |thumb_position| is in the middle of the
   // thumb rather than the top.
   void ScrollToThumbPosition(int thumb_position, bool scroll_to_middle);
 
   // 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:
   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;
 
   // ScrollBar overrides:
   void Update(int viewport_size,
               int content_size,
               int contents_scroll_offset) override;
   int GetLayoutSize() const override = 0;
   int GetPosition() const override;
 
   // ScrollDelegate overrides:
   bool OnScroll(float dx, float dy) override;
 
   // ContextMenuController overrides:
   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:
   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);
 
  private:
   friend class test::ScrollViewTestApi;
 
   FRIEND_TEST_ALL_PREFIXES(ScrollBarViewsTest, ScrollBarFitsToBottom);
   FRIEND_TEST_ALL_PREFIXES(ScrollBarViewsTest, ThumbFullLengthOfTrack);
   int GetThumbSizeForTest();
 
   // Changes to 'pushed' state and starts a timer to scroll repeatedly.
   void ProcessPressEvent(const ui::LocatedEvent& event);
 
-  // Sets state to |state| and stops the repeater.
-  void SetState(CustomButton::ButtonState state);
-
   // Called when the mouse is pressed down in the track area.
   void TrackClicked();
 
   // Responsible for scrolling the contents and also updating the UI to the
   // current value of the Scroll Offset.
   void ScrollContentsToOffset();
 
   // Returns the size (width or height) of the track area of the ScrollBar.
   int GetTrackSize() const;
 
@@ skipping 15 matching lines @@
 
   // The size of the scrolled contents, in pixels.
   int contents_size_;
 
   // The current amount the contents is offset by in the viewport.
   int contents_scroll_offset_;
 
   // The current size of the view port, in pixels.
   int viewport_size_;
 
-  // The state of the scrollbar track. Typically, the track will highlight when
-  // the user presses the mouse on them (during page scrolling).
-  CustomButton::ButtonState thumb_track_state_;
-
   // The last amount of incremental scroll that this scrollbar performed. This
   // is accessed by the callbacks for the auto-repeat up/down buttons to know
   // what direction to repeatedly scroll in.
   ScrollAmount last_scroll_amount_;
 
   // An instance of a RepeatController which scrolls the scrollbar continuously
   // as the user presses the mouse button down on the up/down buttons or the
   // track.
   RepeatController repeater_;
 
   // The position of the mouse within the scroll bar when the context menu
   // was invoked.
   int context_menu_mouse_position_;
 
   std::unique_ptr<MenuRunner> menu_runner_;
   std::unique_ptr<ScrollAnimator> scroll_animator_;
 
   // Difference between current position and cumulative deltas obtained from
   // scroll update events.
   // 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_