Migrated test block 19 to Dart 2.0.

tests/corelib/reg_exp5_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.
-// Dart test for testing regular expressions in Dart.
-
-import "package:expect/expect.dart";
-
-main() {
-  String str = "";
-  try {
-    RegExp ex = new RegExp(str);
-  } catch (e) {
-    if (!(e is ArgumentError)) {
-      Expect.fail("Expected: ArgumentError got: ${e}");
-    }
-  }
-  Expect.isFalse(new RegExp(r"^\w+$").hasMatch(str));
-  Match fm = new RegExp(r"^\w+$").firstMatch(str);
-  Expect.equals(null, fm);
-
-  Iterable<Match> am = new RegExp(r"^\w+$").allMatches(str);
-  Expect.isFalse(am.iterator.moveNext());
-
-  Expect.equals(null, new RegExp(r"^\w+$").stringMatch(str));
-}