Takeover MT initiated animations from the compositor

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

Index: third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
diff --git a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
index 5b625b88bcb94c5507a30e9b1a6f1ce8709eeb48..81519c92079a31e70fb273201e4882bd74ef222b 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -685,9 +685,12 @@ void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainTh
 {
     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