Migrate language/async_backwards... ... language/async_star_take...

tests/language_2/async_regression_23058_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.
 
 // Regression test for issue 23058.
 
 import "package:expect/expect.dart";
 import "package:async_helper/async_helper.dart";
 
 class A {
@@ skipping 16 matching lines @@
   }
 }
 
 main() {
   asyncStart();
   new A().foo().then((result) {
     Expect.equals(1, result);
     asyncEnd();
   });
 }