When using an Object as a set in Object.getOwnPropertyNames, null out the proto

src/v8natives.js

Index: src/v8natives.js
diff --git a/src/v8natives.js b/src/v8natives.js
index 20fc74dc440dcf28dd64ece1de30133611aadf0b..cd7ff78f973a2963d63bfee3eb0413a00911669a 100644
--- a/src/v8natives.js
+++ b/src/v8natives.js
@@ -1025,7 +1025,7 @@ function ObjectGetOwnPropertyNames(obj) {
   }
 
   // Property names are expected to be unique strings.
-  var propertySet = {};
+  var propertySet = { __proto__: null };
   var j = 0;
   for (var i = 0; i < propertyNames.length; ++i) {
     var name = ToString(propertyNames[i]);