Migrate test block 5 to Dart 2.0.

tests/corelib/date_time9_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.
-
-import "package:expect/expect.dart";
-
-main() {
-  var dt = new DateTime.now();
-  Expect.isTrue(dt is Comparable);
-
-  var dt2 = new DateTime.fromMillisecondsSinceEpoch(100);
-  var dt3 = new DateTime.fromMillisecondsSinceEpoch(200, isUtc: true);
-  var dt3b = new DateTime.fromMillisecondsSinceEpoch(200);
-  var dt4 = new DateTime.fromMillisecondsSinceEpoch(300);
-  var dt5 = new DateTime.fromMillisecondsSinceEpoch(400, isUtc: true);
-  var dt5b = new DateTime.fromMillisecondsSinceEpoch(400);
-
-  Expect.isTrue(dt2.compareTo(dt2) == 0);
-  Expect.isTrue(dt3.compareTo(dt3) == 0);
-  Expect.isTrue(dt3b.compareTo(dt3b) == 0);
-  Expect.isTrue(dt4.compareTo(dt4) == 0);
-  Expect.isTrue(dt5.compareTo(dt5) == 0);
-  Expect.isTrue(dt5b.compareTo(dt5b) == 0);
-
-  // Time zones don't have any effect.
-  Expect.isTrue(dt3.compareTo(dt3b) == 0);
-  Expect.isTrue(dt5.compareTo(dt5b) == 0);
-
-  Expect.isTrue(dt2.compareTo(dt3) < 0);
-  Expect.isTrue(dt3.compareTo(dt4) < 0);
-  Expect.isTrue(dt4.compareTo(dt5) < 0);
-
-  Expect.isTrue(dt2.compareTo(dt3b) < 0);
-  Expect.isTrue(dt4.compareTo(dt5b) < 0);
-
-  Expect.isTrue(dt3.compareTo(dt2) > 0);
-  Expect.isTrue(dt4.compareTo(dt3) > 0);
-  Expect.isTrue(dt5.compareTo(dt4) > 0);
-
-  Expect.isTrue(dt3b.compareTo(dt2) > 0);
-  Expect.isTrue(dt5b.compareTo(dt4) > 0);
-}