Run smooth scroll animations on the compositor when possible

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

Index: third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
index dc3a7ca882bf30a320d76c34d6b720683e2947e6..5af07c8e5f9e96bd4ec87fe3df0d4b8472bdf4f8 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollAnimatorCompositorCoordinator.cpp
@@ -52,6 +52,7 @@ bool ScrollAnimatorCompositorCoordinator::hasAnimationThatRequiresService() cons
         return false;
     case RunState::WaitingToSendToCompositor:
     case RunState::RunningOnMainThread:
+    case RunState::RunningOnCompositorButNeedsUpdate:
     case RunState::WaitingToCancelOnCompositor:
         return true;
     }
@@ -84,6 +85,17 @@ void ScrollAnimatorCompositorCoordinator::removeAnimation()
     }
 }
 
+void ScrollAnimatorCompositorCoordinator::abortAnimation()
+{
+    if (m_compositorPlayer) {
+        if (m_compositorPlayer->isLayerAttached())
+            m_compositorPlayer->abortAnimation(m_compositorAnimationId);
+    } else {
+        if (GraphicsLayer* layer = scrollableArea()->layerForScrolling())
+            layer->abortAnimation(m_compositorAnimationId);
+    }
+}
+
 void ScrollAnimatorCompositorCoordinator::cancelAnimation()
 {
     switch (m_runState) {
@@ -101,6 +113,7 @@ void ScrollAnimatorCompositorCoordinator::cancelAnimation()
     case RunState::RunningOnMainThread:
         resetAnimationState();
         break;
+    case RunState::RunningOnCompositorButNeedsUpdate:
     case RunState::RunningOnCompositor:
         m_runState = RunState::WaitingToCancelOnCompositor;
 
@@ -126,6 +139,7 @@ void ScrollAnimatorCompositorCoordinator::compositorAnimationFinished(
     case RunState::WaitingToSendToCompositor:
         break;
     case RunState::RunningOnCompositor:
+    case RunState::RunningOnCompositorButNeedsUpdate:
     case RunState::WaitingToCancelOnCompositor:
         resetAnimationState();
     }