Implement ES6 Array.prototype.toString behind --harmony-tostring

test/mjsunit/es6/object-tostring.js

Index: test/mjsunit/es6/object-tostring.js
diff --git a/test/mjsunit/es6/object-tostring.js b/test/mjsunit/es6/object-tostring.js
index 26dff14b9d29519e24bdc38c6e8d26ae83dc2336..8999a180821cf554e66f4fda4d9e80b74b590775 100644
--- a/test/mjsunit/es6/object-tostring.js
+++ b/test/mjsunit/es6/object-tostring.js
@@ -131,3 +131,9 @@ function testObjectToStringPropertyDesc() {
   assertTrue(desc.configurable);
 }
 testObjectToStringPropertyDesc();
+
+function testObjectToStringOwnNonStringValue() {
+  var obj = Object.defineProperty({}, Symbol.toStringTag, { value: 1 });
+  assertEquals("[object ???]", ({}).toString.call(obj));
+}
+testObjectToStringOwnNonStringValue();