Implement CSSOM Smooth Scroll API

Source/core/dom/Element.h

Index: Source/core/dom/Element.h
diff --git a/Source/core/dom/Element.h b/Source/core/dom/Element.h
index c80686971fb8641e7e8c0d9db065e3dd8e55a0f9..50d91968c7db576879a04a59b66d33ed13a9c346 100644
--- a/Source/core/dom/Element.h
+++ b/Source/core/dom/Element.h
@@ -36,6 +36,7 @@
 #include "core/page/FocusType.h"
 #include "platform/heap/Handle.h"
 #include "platform/scroll/ScrollTypes.h"
+#include "platform/scroll/ScrollableArea.h"
 
 namespace WebCore {
 
@@ -198,10 +199,10 @@ public:
     int clientHeight();
     virtual int scrollLeft();
     virtual int scrollTop();
-    virtual void setScrollLeft(int);
-    virtual void setScrollLeft(const Dictionary& scrollOptionsHorizontal, ExceptionState&);
-    virtual void setScrollTop(int);
-    virtual void setScrollTop(const Dictionary& scrollOptionsVertical, ExceptionState&);
+    void setScrollLeft(int newLeft, ScrollBehavior scrollBehavior = ScrollBehaviorAuto) { setScrollLeftInternal(newLeft, scrollBehavior); }
+    void setScrollLeft(const Dictionary& scrollOptionsHorizontal, ExceptionState&);
+    void setScrollTop(int newTop, ScrollBehavior scrollBehavior = ScrollBehaviorAuto) { setScrollTopInternal(newTop, scrollBehavior); }
+    void setScrollTop(const Dictionary& scrollOptionsVertical, ExceptionState&);
     virtual int scrollWidth();
     virtual int scrollHeight();
 
@@ -553,6 +554,9 @@ protected:
 
     Node* insertAdjacent(const String& where, Node* newChild, ExceptionState&);
 
+    virtual void setScrollLeftInternal(int, ScrollBehavior);
+    virtual void setScrollTopInternal(int, ScrollBehavior);
+
 private:
     bool hasElementFlag(ElementFlags mask) const { return hasRareData() && hasElementFlagInternal(mask); }
     void setElementFlag(ElementFlags, bool value = true);