Fix Mac overlay scrollbars to show when programmatically scrolled.

third_party/WebKit/Source/platform/mac/ScrollAnimatorMac.mm

 /*
  * Copyright (C) 2010, 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 1022 matching lines @@
 
         [m_verticalScrollbarPainterDelegate.get() updateVisibilityImmediately:show];
         [m_verticalScrollbarPainterDelegate.get() updateVisibilityImmediately:show];
         return true;
     }
     return false;
 }
 
 void ScrollAnimatorMac::cancelAnimation()
 {
+    [m_scrollAnimationHelper.get() _stopRun];
     m_haveScrolledSincePageLoad = false;
-
-    if (ScrollbarThemeMacCommon::isOverlayAPIAvailable()) {
-        if (scrollbarPaintTimerIsActive())
-            stopScrollbarPaintTimer();
-        [m_horizontalScrollbarPainterDelegate.get() cancelAnimations];
-        [m_verticalScrollbarPainterDelegate.get() cancelAnimations];
-    }
 }
 
 void ScrollAnimatorMac::handleWheelEventPhase(PlatformWheelEventPhase phase)
 {
     // This may not have been set to true yet if the wheel event was handled by the ScrollingTree,
     // So set it to true here.
     m_haveScrolledSincePageLoad = true;
 
     if (phase == PlatformWheelEventPhaseBegan)
         didBeginScrollGesture();
@@ skipping 117 matching lines @@
         return;
 
     m_visibleScrollerThumbRect = rectInViewCoordinates;
 }
 
 bool ScrollAnimatorMac::canUseCoordinatedScrollbar() {
     return ScrollbarThemeMacCommon::isOverlayAPIAvailable();
 }
 
 } // namespace blink