Update Element API for CSSOM smooth scrolling to match the spec

Source/core/dom/Element.idl

Index: Source/core/dom/Element.idl
diff --git a/Source/core/dom/Element.idl b/Source/core/dom/Element.idl
index 121f7e1e5078da87d1029869e505cb27825d80e2..1e5555ac176ac3ff133929342417ce1fed7109f5 100644
--- a/Source/core/dom/Element.idl
+++ b/Source/core/dom/Element.idl
@@ -69,15 +69,18 @@ interface Element : Node {
     readonly attribute long clientWidth;
     readonly attribute long clientHeight;
 
-    // FIXME: should be:
-    // attribute (Dictionary or double) scrollLeft;
-    // attribute (Dictionary or double) scrollTop;
-    // http://crbug.com/240176
-    [Custom=Setter] attribute double scrollLeft;
-    [Custom=Setter] attribute double scrollTop;
+    attribute double scrollLeft;
+    attribute double scrollTop;
     readonly attribute long scrollWidth;
     readonly attribute long scrollHeight;
 
+    [RuntimeEnabled=CSSOMSmoothScroll] void scroll(double x, double y);
+    [RuntimeEnabled=CSSOMSmoothScroll] void scroll(optional ScrollToOptions scrollToOptions);
+    [RuntimeEnabled=CSSOMSmoothScroll] void scrollTo(double x, double y);
+    [RuntimeEnabled=CSSOMSmoothScroll] void scrollTo(optional ScrollToOptions scrollToOptions);
+    [RuntimeEnabled=CSSOMSmoothScroll] void scrollBy(double x, double y);
+    [RuntimeEnabled=CSSOMSmoothScroll] void scrollBy(optional ScrollToOptions scrollToOptions);
+
     void focus();
     void blur();
     void scrollIntoView(optional boolean alignWithTop);