Run smooth scroll animations on the compositor when possible

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

Index: third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
index 77996f3cb6d58c467fcd15caf227d5c546e7f80a..02635bed263571b4cead5bda12dee4e6c0350bf1 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableArea.cpp
@@ -454,6 +454,8 @@ void ScrollableArea::layerForScrollingDidChange(WebCompositorAnimationTimeline*
 {
     if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
         programmaticScrollAnimator->layerForCompositedScrollingDidChange(timeline);
+    if (ScrollAnimatorBase* scrollAnimator = existingScrollAnimator())
+        scrollAnimator->layerForCompositedScrollingDidChange(timeline);
 }
 
 bool ScrollableArea::scheduleAnimation()
@@ -469,8 +471,8 @@ void ScrollableArea::serviceScrollAnimations(double monotonicTime)
 {
     bool requiresAnimationService = false;
     if (ScrollAnimatorBase* scrollAnimator = existingScrollAnimator()) {
-        scrollAnimator->serviceScrollAnimations();
-        if (scrollAnimator->hasRunningAnimation())
+        scrollAnimator->tickAnimation(monotonicTime);
+        if (scrollAnimator->hasAnimationThatRequiresService())
             requiresAnimationService = true;
     }
     if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator()) {
@@ -486,18 +488,24 @@ void ScrollableArea::updateCompositorScrollAnimations()
 {
     if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
         programmaticScrollAnimator->updateCompositorAnimations();
+
+    if (ScrollAnimatorBase* scrollAnimator = existingScrollAnimator())
+        scrollAnimator->updateCompositorAnimations();
 }
 
 void ScrollableArea::notifyCompositorAnimationFinished(int groupId)
 {
     if (ProgrammaticScrollAnimator* programmaticScrollAnimator = existingProgrammaticScrollAnimator())
         programmaticScrollAnimator->notifyCompositorAnimationFinished(groupId);
+
+    if (ScrollAnimatorBase* scrollAnimator = existingScrollAnimator())
+        scrollAnimator->notifyCompositorAnimationFinished(groupId);
 }
 
 void ScrollableArea::cancelScrollAnimation()
 {
     if (ScrollAnimatorBase* scrollAnimator = existingScrollAnimator())
-        scrollAnimator->cancelAnimations();
+        scrollAnimator->cancelAnimation();
 }
 
 void ScrollableArea::cancelProgrammaticScrollAnimation()