Send takeover msg from MT to CC using the animation path.

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 ce5e657576bff88ba0c2a008aa42ee4faa33a5d0..f1db243447f3388e81d0dec66fc92f1e5d792001 100644
--- a/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
+++ b/third_party/WebKit/Source/core/page/scrolling/ScrollingCoordinator.cpp
@@ -664,8 +664,10 @@ void ScrollingCoordinator::setShouldUpdateScrollLayerPositionOnMainThread(MainTh
     if (WebLayer* scrollLayer = toWebLayer(layer)) {
         m_lastMainThreadScrollingReasons = mainThreadScrollingReasons;
         if (mainThreadScrollingReasons) {
-            if (ScrollAnimatorBase* scrollAnimator = layer->getScrollableArea()->existingScrollAnimator())
+            if (ScrollAnimatorBase* scrollAnimator = layer->getScrollableArea()->existingScrollAnimator()) {
+                scrollAnimator->takeoverImplOnlyScrollOffsetAnimation();
                 scrollAnimator->takeoverCompositorAnimation();

[skobes, 2016/05/24 23:50:50]

Perhaps takeoverImplOnlyScrollOffsetAnimation can be combined with
takeoverCompositorAnimation?

[ymalik, 2016/05/25 16:09:05]

Yeah! That's actually more correct because we either have an animation running
on cc or on mt, so shouldn't be doing both.

+            }
             scrollLayer->addMainThreadScrollingReasons(mainThreadScrollingReasons);
         } else {
             // Clear all main thread scrolling reasons except the one that's set