Add the ability to change the working directory

utils/tests/testrunner/testrunner_test.dart

 // Copyright (c) 2013, 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 testrunner_test;
 
 import 'dart:async';
 import 'dart:io';
 import 'package:unittest/unittest.dart';
 
@@ skipping 494 matching lines @@
     });
   });
 
   group("embedded server", () {
     test("get test", () {
       return runTest(
         [ testrunner,
           '--recurse',
           '--server',
           '--port=3456',
-          '--root=${new Directory.current().path}',
+          '--root=${Directory.current.path}',
           'http_client_tests' ],
         [ '?PASS .*/http_client_tests/http_client_test.dart  test1',
           '?PASS .*/http_client_tests/http_client_test.dart  test2' ]);
     });
   });
 }