Fix js/null_test to run also in CSP mode

tests/lib/js/null_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library null_test;
 
 import 'dart:js';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
 main() {
   useHtmlConfiguration();
   test('null is sent as null', () {
     expect(context['isNull'].apply([null]), isTrue);
     expect(context['isUndefined'].apply([null]), isFalse);
   });
 }