Implement CSSOM smooth scroll for Elements

Source/platform/scroll/ScrollAnimatorNone.cpp

Index: Source/platform/scroll/ScrollAnimatorNone.cpp
diff --git a/Source/platform/scroll/ScrollAnimatorNone.cpp b/Source/platform/scroll/ScrollAnimatorNone.cpp
index 107851ae94f9620b905f5724d02a3cc441f0794d..5791e2e8798192686956889c59e3fdafb2b89a82 100644
--- a/Source/platform/scroll/ScrollAnimatorNone.cpp
+++ b/Source/platform/scroll/ScrollAnimatorNone.cpp
@@ -428,6 +428,7 @@ bool ScrollAnimatorNone::scroll(ScrollbarOrientation orientation, ScrollGranular
         m_startTime = data.m_startTime;
         animationWillStart();
         animationTimerFired();
+        scrollableArea()->registerForAnimation();
     }
     return needToScroll;
 }
@@ -460,6 +461,11 @@ void ScrollAnimatorNone::serviceScrollAnimations()
         animationTimerFired();
 }
 
+bool ScrollAnimatorNone::hasRunningAnimation() const
+{
+    return m_animationActive;
+}
+
 void ScrollAnimatorNone::willEndLiveResize()
 {
     updateVisibleLengths();