Migrated test block 19 to Dart 2.0.

tests/corelib_2/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();
 }