Add remaining @@toStringTag symbols to builtins

test/mjsunit/es6/string-iterator.js

Index: test/mjsunit/es6/string-iterator.js
diff --git a/test/mjsunit/es6/string-iterator.js b/test/mjsunit/es6/string-iterator.js
index e6bea6dfe76a286b7c7e22cf632e9ad389c5a46a..769f549254d602362487181650509fdb34b6332f 100644
--- a/test/mjsunit/es6/string-iterator.js
+++ b/test/mjsunit/es6/string-iterator.js
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// Flags: --harmony-tostring
 
 function TestStringPrototypeIterator() {
   assertTrue(String.prototype.hasOwnProperty(Symbol.iterator));
@@ -59,6 +60,12 @@ function TestStringIteratorPrototype() {
   assertArrayEquals(['next'],
       Object.getOwnPropertyNames(StringIteratorPrototype));
   assertEquals('[object String Iterator]', "" + iterator);
+  assertEquals("String Iterator", StringIteratorPrototype[Symbol.toStringTag]);
+  var desc = Object.getOwnPropertyDescriptor(
+      StringIteratorPrototype, Symbol.toStringTag);
+  assertTrue(desc.configurable);
+  assertFalse(desc.writable);
+  assertEquals("String Iterator", desc.value);
 }
 TestStringIteratorPrototype();