Implement CSSOM smooth scroll for Elements

Source/platform/scroll/ScrollAnimatorNone.cpp

 /*
  * Copyright (c) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 410 matching lines @@
 
     // This is an animatable scroll. Set the animation in motion using the appropriate parameters.
     float scrollableSize = static_cast<float>(m_scrollableArea->scrollSize(orientation));
 
     PerAxisData& data = (orientation == VerticalScrollbar) ? m_verticalData : m_horizontalData;
     bool needToScroll = data.updateDataFromParameters(step, delta, scrollableSize, WTF::monotonicallyIncreasingTime(), &parameters);
     if (needToScroll && !animationTimerActive()) {
         m_startTime = data.m_startTime;
         animationWillStart();
         animationTimerFired();
+        scrollableArea()->registerForAnimation();
     }
     return needToScroll;
 }
 
 void ScrollAnimatorNone::scrollToOffsetWithoutAnimation(const FloatPoint& offset)
 {
     stopAnimationTimerIfNeeded();
 
     m_horizontalData.reset();
     *m_horizontalData.m_currentPosition = offset.x();
@@ skipping 12 matching lines @@
 {
     m_animationActive = false;
 }
 
 void ScrollAnimatorNone::serviceScrollAnimations()
 {
     if (m_animationActive)
         animationTimerFired();
 }
 
+bool ScrollAnimatorNone::hasRunningAnimation() const
+{
+    return m_animationActive;
+}
+
 void ScrollAnimatorNone::willEndLiveResize()
 {
     updateVisibleLengths();
 }
 
 void ScrollAnimatorNone::didAddVerticalScrollbar(Scrollbar*)
 {
     updateVisibleLengths();
 }
 
@@ skipping 43 matching lines @@
     return m_animationActive;
 }
 
 void ScrollAnimatorNone::stopAnimationTimerIfNeeded()
 {
     if (animationTimerActive())
         m_animationActive = false;
 }
 
 } // namespace blink