Revert of Implement overlay scrollbar fade out for non-composited scrollers.

third_party/WebKit/Source/platform/scroll/ScrollableArea.h

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
index c23d25157f7d92edcfad150b9fde72acbf523b45..2de87e1c4717c03d7d404e07f1f2173a8066f0e4 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.h
@@ -109,10 +109,8 @@
   void mouseEnteredContentArea() const;
   void mouseExitedContentArea() const;
   void mouseMovedInContentArea() const;
-  void mouseEnteredScrollbar(Scrollbar&);
-  void mouseExitedScrollbar(Scrollbar&);
-  void mouseCapturedScrollbar();
-  void mouseReleasedScrollbar();
+  void mouseEnteredScrollbar(Scrollbar&) const;
+  void mouseExitedScrollbar(Scrollbar&) const;
   void contentAreaDidShow() const;
   void contentAreaDidHide() const;
 
@@ -231,6 +229,7 @@
 
   virtual bool shouldSuspendScrollAnimations() const { return true; }
   virtual void scrollbarStyleChanged() {}
+  virtual void scrollbarVisibilityChanged() {}
   virtual bool scrollbarsCanBeActive() const = 0;
 
   // Returns the bounding box of this scrollable area, in the coordinate system
@@ -259,6 +258,7 @@
   // Overlay scrollbars can "fade-out" when inactive.
   virtual bool scrollbarsHidden() const;
   virtual void setScrollbarsHidden(bool);
+  virtual void didChangeScrollbarsHidden(){};
 
   // Returns true if the GraphicsLayer tree needs to be rebuilt.
   virtual bool updateAfterCompositingChange() { return false; }
@@ -358,7 +358,7 @@
   EAGERLY_FINALIZE();
   DECLARE_VIRTUAL_TRACE();
 
-  virtual void clearScrollableArea();
+  virtual void clearScrollAnimators();
 
   virtual ScrollAnchor* scrollAnchor() { return nullptr; }
 
@@ -390,14 +390,10 @@
     m_verticalScrollbarNeedsPaintInvalidation = false;
     m_scrollCornerNeedsPaintInvalidation = false;
   }
-  void showOverlayScrollbars();
-  virtual void scrollbarVisibilityChanged() {}
 
  private:
   void programmaticScrollHelper(const ScrollOffset&, ScrollBehavior);
   void userScrollHelper(const ScrollOffset&, ScrollBehavior);
-
-  void fadeOverlayScrollbarsTimerFired(TimerBase*);
 
   // This function should be overriden by subclasses to perform the actual
   // scroll of the content.
@@ -411,8 +407,6 @@
   mutable Member<ScrollAnimatorBase> m_scrollAnimator;
   mutable Member<ProgrammaticScrollAnimator> m_programmaticScrollAnimator;
 
-  std::unique_ptr<Timer<ScrollableArea>> m_fadeOverlayScrollbarsTimer;
-
   unsigned m_scrollbarOverlayColorTheme : 2;
 
   unsigned m_scrollOriginChanged : 1;
@@ -421,7 +415,6 @@
   unsigned m_verticalScrollbarNeedsPaintInvalidation : 1;
   unsigned m_scrollCornerNeedsPaintInvalidation : 1;
   unsigned m_scrollbarsHidden : 1;
-  unsigned m_scrollbarCaptured : 1;
 
   // There are 6 possible combinations of writing mode and direction. Scroll
   // origin will be non-zero in the x or y axis if there is any reversed