Migrated test block 27 to Dart 2.0.

tests/corelib_strong/stopwatch2_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.
-
-// Dart test program for elapsed getters in stopwatch support.
-
-import "package:expect/expect.dart";
-
-main() {
-  Stopwatch sw = new Stopwatch()..start();
-  while (sw.elapsedMilliseconds < 2) {
-    /* do nothing. */
-  }
-  sw.stop();
-  Expect.equals(sw.elapsedMicroseconds, sw.elapsed.inMicroseconds);
-  Expect.equals(sw.elapsedMilliseconds, sw.elapsed.inMilliseconds);
-}