Takeover MT initiated animations from the compositor

third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 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 653 matching lines @@
 
 void ScrollingCoordinator::willDestroyLayer(PaintLayer* layer)
 {
     m_layersWithTouchRects.remove(layer);
 }
 
 void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainThreadScrollingReasons mainThreadScrollingReasons)
 {
     if (!m_page->mainFrame()->isLocalFrame() || !m_page->deprecatedLocalMainFrame()->view())
         return;
-    if (WebLayer* scrollLayer = toWebLayer(m_page->deprecatedLocalMainFrame()->view()->layerForScrolling())) {
+    GraphicsLayer* layer = m_page->deprecatedLocalMainFrame()->view()->layerForScrolling();
+    if (WebLayer* scrollLayer = toWebLayer(layer)) {
         m_lastMainThreadScrollingReasons = mainThreadScrollingReasons;
         if (mainThreadScrollingReasons) {
+            if (ScrollAnimatorBase* scrollAnimator = layer->scrollableArea()->existingScrollAnimator())
+                scrollAnimator->takeoverCompositorAnimation();
             scrollLayer->addMainThreadScrollingReasons(mainThreadScrollingReasons);
         } else {
             // Clear all main thread scrolling reasons except the one that's set
             // if there is a running scroll animation.
             uint32_t mainThreadScrollingReasonsToClear = ~0u;
             mainThreadScrollingReasonsToClear &= ~MainThreadScrollingReason::kAnimatingScrollOnMainThread;
             scrollLayer->clearMainThreadScrollingReasons(mainThreadScrollingReasonsToClear);
         }
     }
 }
@@ skipping 360 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : nullptr)
         return WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace blink