Removing test for exceptions being thrown from MessageEvent.

tests/html/serialized_script_value_test.dart

 library SerializedScriptValueTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 import 'utils.dart';
 
 serializationTest(name, value) => test(name, () {
     // To check how value is serialized and deserialized, we create a
     // MessageEvent.
     final event =
@@ skipping 31 matching lines @@
   var blob = new Blob(
       ['Indescribable... Indestructible! Nothing can stop it!'],
       'text/plain');
   serializationTest('blob', [blob]);
 
   var canvas = new CanvasElement();
   canvas.width = 100;
   canvas.height = 100;
   var imageData = canvas.context2D.getImageData(0, 0, 1, 1);
   serializationTest('imagedata', [imageData]);
-
-  expect(() {
-    new MessageEvent('', data: new DivElement(), origin: '', lastEventId: '');
-  }, throws);
 }