Run smooth scroll animations on the compositor when possible

third_party/WebKit/Source/platform/scroll/ScrollAnimator.h

Index: third_party/WebKit/Source/platform/scroll/ScrollAnimator.h
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollAnimator.h b/third_party/WebKit/Source/platform/scroll/ScrollAnimator.h
index 01746e683e176296ad1cc6b591801b1803e85b90..5d8f20a3f84d00c41494120eae3ec0b660651b00 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollAnimator.h
+++ b/third_party/WebKit/Source/platform/scroll/ScrollAnimator.h
@@ -34,11 +34,14 @@
 #include "platform/Timer.h"
 #include "platform/geometry/FloatPoint.h"
 #include "platform/scroll/ScrollAnimatorBase.h"
+#include "public/platform/WebCompositorAnimationDelegate.h"
+#include "public/platform/WebCompositorAnimationPlayerClient.h"
 #include "public/platform/WebScrollOffsetAnimationCurve.h"
 
 namespace blink {
 
 class ScrollAnimatorTest;
+class WebCompositorAnimationTimeline;
 
 class PLATFORM_EXPORT ScrollAnimator final : public ScrollAnimatorBase {
 public:
@@ -50,20 +53,26 @@ public:
     ScrollResultOneDimensional userScroll(ScrollbarOrientation, ScrollGranularity, float step, float delta) override;
     void scrollToOffsetWithoutAnimation(const FloatPoint&) override;
 
-    void cancelAnimations() override;
-    void serviceScrollAnimations() override;
-    bool hasRunningAnimation() const override;
+    // ScrollAnimatorCompositorCoordinator implementation.
+    void tickAnimation(double monotonicTime) override;
+    void cancelAnimation() override;
+    void resetAnimationState() override;
+    void updateCompositorAnimations() override;
+    void notifyCompositorAnimationFinished(int groupId) override;
+    void layerForCompositedScrollingDidChange(WebCompositorAnimationTimeline*) override;
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
-    void animationTimerFired();
-
     OwnPtr<WebScrollOffsetAnimationCurve> m_animationCurve;
+    double m_lastTickTime;
     double m_startTime;
     WTF::TimeFunction m_timeFunction;
+
 private:
     FloatPoint desiredTargetPosition() const;
+
+    FloatPoint m_targetOffset;
 };
 
 } // namespace blink