Migrated test block 19 to Dart 2.0.

tests/corelib/reg_exp_groups_test.dart

-// Copyright (c) 2011, 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";
-
-// Dart test program for RegExp.groups.
-
-class RegExpGroupsTest {
-  static testMain() {
-    var match = new RegExp("(a(b)((c|de)+))").firstMatch("abcde");
-    var groups = match.groups([0, 4, 2, 3]);
-    Expect.equals('abcde', groups[0]);
-    Expect.equals('de', groups[1]);
-    Expect.equals('b', groups[2]);
-    Expect.equals('cde', groups[3]);
-  }
-}
-
-main() {
-  RegExpGroupsTest.testMain();
-}