Reapply r6925 with fixed status file.

client/tests/client/html/XHRTests.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.
-
-
-void testXHR() {
-  print(window.location.href);
-  asyncTest('XHR', 1, () {
-    XMLHttpRequest xhr = new XMLHttpRequest();
-    xhr.open("GET", "NonExistingFile", true);
-    xhr.on.readyStateChange.add((event) {
-        if (xhr.readyState == 4) {
-          Expect.equals(0, xhr.status);
-          Expect.stringEquals('', xhr.responseText);
-          callbackDone();
-        }
-      });
-    xhr.send();
-  });
-}