auto merge of #2649 : ebalint/servo/2580_JS_T_unrooted_replace, r=jdm

removed .clone() calls
modified from_rooted method parameter: T to &T

src/components/script/dom/attr.rs

@@ -84,7 +84,7 @@ impl Attr {
             name: name, //TODO: Intern attribute names
             namespace: namespace,
             prefix: prefix,
-            owner: Cell::new(owner.unrooted()),
+            owner: Cell::new(JS::from_rooted(owner)),
         }
     }