Fix Element missing attributes

Attributes classList and attributes are [SameObject].
servo · bors-servo · Sep 20, 2015 · Sep 11, 2015 · Sep 11, 2015 · Sep 11, 2015
commit d93c8da7d74d51f87a2254adf848ac5fd171338f
diff --git a/components/script/dom/webidls/Element.webidl b/components/script/dom/webidls/Element.webidl
@@ -28,10 +28,10 @@ interface Element : Node {
            attribute DOMString id;
   [Pure]
            attribute DOMString className;
-  [Constant]
+  [SameObject]
   readonly attribute DOMTokenList classList;
 
-  [Constant]
+  [SameObject]
   readonly attribute NamedNodeMap attributes;
   DOMString? getAttribute(DOMString name);
   DOMString? getAttributeNS(DOMString? namespace, DOMString localName);