Migrated test block 19 to Dart 2.0.

tests/corelib_strong/reg_exp_string_match_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.stringMatch.
-
-class RegExpStringMatchTest {
-  static testMain() {
-    Expect.equals('cat', new RegExp("(\\w+)").stringMatch("cat dog"));
-    Expect.equals(null, new RegExp("foo").stringMatch("bar"));
-  }
-}
-
-main() {
-  RegExpStringMatchTest.testMain();
-}