DOMException toString is not correct

LayoutTests/fast/dom/DOMException/resources/dispatch-event-exception.js

 description("Tests the properties of the exception thrown by dispatchEvent.")
 
 var e;
 try {
     document.dispatchEvent(null);
     // raises a InvalidStateError
 } catch (err) {
     e = err;
 }
 
-shouldBeEqualToString("e.toString()", "Error: InvalidStateError: DOM Exception 11");
+shouldBeEqualToString("e.toString()", "InvalidStateError: An attempt was made to use an object that is not, or is no longer, usable.");
 shouldBeEqualToString("Object.prototype.toString.call(e)", "[object DOMException]");
 shouldBeEqualToString("Object.prototype.toString.call(e.__proto__)", "[object DOMExceptionPrototype]");
 shouldBeEqualToString("e.constructor.toString()", "function DOMException() { [native code] }");
 shouldBe("e.constructor", "window.DOMException");