Implement CSSOM smooth scroll for Elements

Source/core/frame/FrameView.cpp

 /*
  * Copyright (C) 1998, 1999 Torben Weis <weis@kde.org>
  *                     1999 Lars Knoll <knoll@kde.org>
  *                     1999 Antti Koivisto <koivisto@kde.org>
  *                     2000 Dirk Mueller <mueller@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *           (C) 2006 Graham Dennis (graham.dennis@gmail.com)
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
@@ skipping 2889 matching lines @@
     m_scrollableAreas->add(scrollableArea);
 }
 
 void FrameView::removeScrollableArea(ScrollableArea* scrollableArea)
 {
     if (!m_scrollableAreas)
         return;
     m_scrollableAreas->remove(scrollableArea);
 }
 
+void FrameView::addAnimatingScrollableArea(ScrollableArea* scrollableArea)
+{
+    ASSERT(scrollableArea);
+    if (!m_animatingScrollableAreas)
+        m_animatingScrollableAreas = adoptPtr(new ScrollableAreaSet);
+    m_animatingScrollableAreas->add(scrollableArea);
+}
+
+void FrameView::removeAnimatingScrollableArea(ScrollableArea* scrollableArea)
+{
+    if (!m_animatingScrollableAreas)
+        return;
+    m_animatingScrollableAreas->remove(scrollableArea);
+}
+
 void FrameView::setParent(Widget* parentView)
 {
     if (parentView == parent())
         return;
 
     if (m_scrollbarsAvoidingResizer && parent())
         toFrameView(parent())->adjustScrollbarsAvoidingResizerCount(-m_scrollbarsAvoidingResizer);
 
     Widget::setParent(parentView);
 
@@ skipping 1046 matching lines @@
         return;
 
     ScrollableArea::setScrollOrigin(origin);
 
     // Update if the scroll origin changes, since our position will be different if the content size did not change.
     if (updatePositionAtAll && updatePositionSynchronously)
         updateScrollbars(scrollOffsetDouble());
 }
 
 } // namespace blink