Migrate test block 5 to Dart 2.0.

tests/corelib_2/date_time10_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.
 
 import "package:expect/expect.dart";
 
 // Make sure the years in the range of single digits are handled correctly with
 // month roll-over. (This tests an edge condition when delegating to
 // JavaScript's Date constructor.)
 
@@ skipping 34 matching lines @@
 
   check("0005-03-02 00:00:00.000", new DateTime(4, 2 + 12, 30));
   check("0005-03-02 00:00:00.000", new DateTime(5, 2, 30));
   check("0005-03-02 00:00:00.000", new DateTime(6, 2 - 12, 30));
 }
 
 main() {
   testUtc();
   testLocal();
 }