Feed ScrollableArea::showOverlayScrollbars into ScrollbarAnimationController.

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

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
@@ skipping 49 matching lines @@
 }
 
 ScrollableArea::ScrollableArea()
     : m_scrollbarOverlayColorTheme(ScrollbarOverlayColorThemeDark),
       m_scrollOriginChanged(false),
       m_horizontalScrollbarNeedsPaintInvalidation(false),
       m_verticalScrollbarNeedsPaintInvalidation(false),
       m_scrollCornerNeedsPaintInvalidation(false),
       m_scrollbarsHidden(false),
       m_scrollbarCaptured(false),
-      m_mouseOverScrollbar(false) {}
+      m_mouseOverScrollbar(false),
+      m_needsShowScrollbarLayers(false) {}
 
 ScrollableArea::~ScrollableArea() {}
 
 void ScrollableArea::clearScrollableArea() {
 #if OS(MACOSX)
   if (m_scrollAnimator)
     m_scrollAnimator->dispose();
 #endif
   m_scrollAnimator.clear();
   m_programmaticScrollAnimator.clear();
@@ skipping 477 matching lines @@
 
 void ScrollableArea::fadeOverlayScrollbarsTimerFired(TimerBase*) {
   setScrollbarsHidden(true);
 }
 
 void ScrollableArea::showOverlayScrollbars() {
   if (!ScrollbarTheme::theme().usesOverlayScrollbars())
     return;
 
   setScrollbarsHidden(false);
+  m_needsShowScrollbarLayers = true;
 
   const double timeUntilDisable =
       ScrollbarTheme::theme().overlayScrollbarFadeOutDelaySeconds() +
       ScrollbarTheme::theme().overlayScrollbarFadeOutDurationSeconds();
 
   // If the overlay scrollbars don't fade out, don't do anything. This is the
   // case for the mock overlays used in tests and on Mac, where the fade-out is
   // animated in ScrollAnimatorMac.
   if (!timeUntilDisable)
     return;
@@ skipping 89 matching lines @@
                                         offset.y() - scrollOrigin().y());
   setScrollOffset(newOffset, CompositorScroll);
 }
 
 DEFINE_TRACE(ScrollableArea) {
   visitor->trace(m_scrollAnimator);
   visitor->trace(m_programmaticScrollAnimator);
 }
 
 }  // namespace blink