Implement CSSOM Smooth Scroll API

Source/core/rendering/RenderLayerScrollableArea.h

Index: Source/core/rendering/RenderLayerScrollableArea.h
diff --git a/Source/core/rendering/RenderLayerScrollableArea.h b/Source/core/rendering/RenderLayerScrollableArea.h
index 2742605d2be29f8b7d554802c2adcd76bb7a994b..ee941a9730102da40f75569838d5ca6f0f61ec3e 100644
--- a/Source/core/rendering/RenderLayerScrollableArea.h
+++ b/Source/core/rendering/RenderLayerScrollableArea.h
@@ -105,6 +105,10 @@ public:
     virtual bool shouldPlaceVerticalScrollbarOnLeft() const OVERRIDE;
     virtual int pageStep(ScrollbarOrientation) const OVERRIDE;
 
+    virtual void registerForAnimation() OVERRIDE;
+    virtual void deregisterForAnimation() OVERRIDE;
+    virtual bool scheduleAnimation() OVERRIDE;
+
     int scrollXOffset() const { return m_scrollOffset.width() + scrollOrigin().x(); }
     int scrollYOffset() const { return m_scrollOffset.height() + scrollOrigin().y(); }
 
@@ -113,9 +117,15 @@ public:
     // FIXME: We shouldn't allow access to m_overflowRect outside this class.
     LayoutRect overflowRect() const { return m_overflowRect; }
 
-    void scrollToOffset(const IntSize& scrollOffset, ScrollOffsetClamping = ScrollOffsetUnclamped);
-    void scrollToXOffset(int x, ScrollOffsetClamping clamp = ScrollOffsetUnclamped) { scrollToOffset(IntSize(x, scrollYOffset()), clamp); }
-    void scrollToYOffset(int y, ScrollOffsetClamping clamp = ScrollOffsetUnclamped) { scrollToOffset(IntSize(scrollXOffset(), y), clamp); }
+    void scrollToOffset(const IntSize& scrollOffset, ScrollOffsetClamping = ScrollOffsetUnclamped, ScrollBehavior = ScrollBehaviorInstant);
+    void scrollToXOffset(int x, ScrollOffsetClamping clamp = ScrollOffsetUnclamped, ScrollBehavior scrollBehavior = ScrollBehaviorInstant)
+    {
+        scrollToOffset(IntSize(x, scrollYOffset()), clamp, scrollBehavior);
+    }
+    void scrollToYOffset(int y, ScrollOffsetClamping clamp = ScrollOffsetUnclamped, ScrollBehavior scrollBehavior = ScrollBehaviorInstant)
+    {
+        scrollToOffset(IntSize(scrollXOffset(), y), clamp, scrollBehavior);
+    }
 
     void updateAfterLayout();
     void updateAfterStyleChange(const RenderStyle*);