auto merge of #4050 : mttr/servo/implement_attr_nodevalue, r=Ms2ger

Fixes #4047, and updates to expect tests that are now passing because of it.

components/script/dom/attr.rs

@@ -152,6 +152,14 @@ impl<'a> AttrMethods for JSRef<'a, Attr> {
         self.SetValue(value)
     }
 
+    fn NodeValue(self) -> DOMString {
+        self.Value()
+    }
+
+    fn SetNodeValue(self, value: DOMString) {
+        self.SetValue(value)
+    }
+
     fn Name(self) -> DOMString {
         self.name.as_slice().to_string()
     }

components/script/dom/webidls/Attr.webidl

@@ -15,6 +15,7 @@ interface Attr {
   readonly attribute DOMString name;
            attribute DOMString value;
            attribute DOMString textContent; // alias of .value
+           attribute DOMString nodeValue; // alias of .value
 
   readonly attribute Element? ownerElement;