More Gecko 2 fixes.

--HG--
branch : testing

common/content/util.js

@@ -417,11 +417,12 @@ const Util = Module("util", {
             null
         );
 
-        result.__iterator__ = asIterator
+        return {
+                __proto__: result,
+                __iterator__: asIterator
                             ? function () { let elem; while ((elem = this.iterateNext())) yield elem; }
-                            : function () { for (let i = 0; i < this.snapshotLength; i++) yield this.snapshotItem(i); };
+                            : function () { for (let i = 0; i < this.snapshotLength; i++) yield this.snapshotItem(i); }
-
+        }
-        return result;
     },
 
     /**