Bug 1131796. Don't parent the DOM proxy expando object to the proxy. r=peterv

dom/bindings/DOMJSProxyHandler.cpp

@@ -112,9 +112,8 @@ DOMProxyHandler::EnsureExpandoObject(JSContext* cx, JS::Handle<JSObject*> obj)
     expandoAndGeneration = nullptr;
   }
 
-  JS::Rooted<JSObject*> parent(cx, js::GetObjectParent(obj));
   JS::Rooted<JSObject*> expando(cx,
-    JS_NewObjectWithGivenProto(cx, nullptr, JS::NullPtr(), parent));
+    JS_NewObjectWithGivenProto(cx, nullptr, JS::NullPtr()));
   if (!expando) {
     return nullptr;
   }