Add cross-origin test with credentials.

tests/html/xhr_test.dart

 // Copyright (c) 2012, 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 XHRTest;
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 import 'dart:html';
 import 'dart:json';
 
@@ skipping 12 matching lines @@
     xhr.send();
   });
 
   test('XHR.get No file', () {
     new HttpRequest.get("NonExistingFile", expectAsync1((xhr) {
       expect(xhr.readyState, equals(HttpRequest.DONE));
       expect(xhr.status, equals(0));
       expect(xhr.responseText, equals(''));
     }));
   });
+
+  test('XHR.getWithCredentials No file', () {
+    new HttpRequest.getWithCredentials("NonExistingFile", expectAsync1((xhr) {
+      expect(xhr.readyState, equals(HttpRequest.DONE));
+      expect(xhr.status, equals(0));
+      expect(xhr.responseText, equals(''));
+    }));
+  });
 }