Migrated test block 19 to Dart 2.0.

tests/corelib_2/regexp/default_arguments_test.dart

 // Copyright (c) 2015, 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.
 
 // Test that `null` is interpreted as `false` when passed as argument to
 // `caseSensitive` and `multiLine`.
 
 import 'package:expect/expect.dart';
 
 main() {
@@ skipping 15 matching lines @@
 testMultiLine() {
   var r1 = new RegExp(r'^foo$');
   var r2 = new RegExp(r'^foo$', multiLine: true);
   var r3 = new RegExp(r'^foo$', multiLine: false);
   var r4 = new RegExp(r'^foo$', multiLine: null);
   Expect.isNull(r1.firstMatch('\nfoo\n'), "r1.firstMatch('\\nfoo\\n')");
   Expect.isNotNull(r2.firstMatch('\nfoo\n'), "r2.firstMatch('\\nfoo\\n')");
   Expect.isNull(r3.firstMatch('\nfoo\n'), "r3.firstMatch('\\nfoo\\n')");
   Expect.isNull(r4.firstMatch('\nfoo\n'), "r4.firstMatch('\\nfoo\\n')");
 }