Migrated test block 19 to Dart 2.0.

tests/corelib_2/regexp/capture-3_test.dart

 // Copyright (c) 2014, the Dart project authors. All rights reserved.
 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
@@ skipping 110 matching lines @@
   regex10.firstMatch(input0);
 
   var regex11 = new RegExp(r"^(?:[^\u0000-\u0080]|[0-9a-z?,.!&\s#()])+$",
       caseSensitive: false);
   regex11.firstMatch(input0);
 
   var regex12 = new RegExp(
       r"u(\xf0{8}?\D*?|( ? !)$h??(|)*?(||)+?\6((?:\W\B|--\d-*-|)?$){0, }?|^Y( ? !1)\d+)+a");
   regex12.firstMatch("");
 }