Migrated test block 28 to Dart 2.0.

tests/corelib_2/string_split_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";
 
 main() {
   testSplitString();
   testSplitRegExp();
   testSplitPattern();
@@ skipping 115 matching lines @@
   final regexp;
   RegExpWrap(String source) : regexp = new RegExp(source);
   Iterable<Match> allMatches(String string, [int start = 0]) =>
       regexp.allMatches(string, start);
 
   Match matchAsPrefix(String string, [int start = 0]) =>
       regexp.matchAsPrefix(string, start);
 
   String toString() => "Wrap(/${regexp.pattern}/)";
 }