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

tests/language_strong/async_star_cancel_while_paused_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.
-
-// This is a regression test for issue 22853.
-
-import "dart:async";
-import "package:expect/expect.dart";
-import "package:async_helper/async_helper.dart";
-
-main() {
-  var list = [];
-  var sync = new Sync();
-  f() async* {
-    list.add("*1");
-    yield 1;
-    await sync.wait();
-    sync.release();
-    list.add("*2");
-    yield 2;
-    list.add("*3");
-  }
-
-  ;
-  var stream = f();
-  var sub = stream.listen(list.add);
-
-  asyncStart();
-  return sync.wait().whenComplete(() {
-    Expect.listEquals(list, ["*1", 1]);
-    sub.pause();
-    return sync.wait();
-  }).whenComplete(() {
-    Expect.listEquals(list, ["*1", 1, "*2"]);
-    sub.cancel();
-    new Future.delayed(new Duration(milliseconds: 200), () {
-      // Should not have yielded 2 or added *3 while paused.
-      Expect.listEquals(list, ["*1", 1, "*2"]);
-      asyncEnd();
-    });
-  });
-}
-
-/**
- * Allows two asynchronous executions to synchronize.
- *
- * Calling [wait] and waiting for the returned future to complete will
- * wait for the other executions to call [wait] again. At that point,
- * the waiting execution is allowed to continue (the returned future completes),
- * and the more recent call to [wait] is now the waiting execution.
- */
-class Sync {
-  Completer _completer = null;
-  // Release whoever is currently waiting and start waiting yourself.
-  Future wait([v]) {
-    if (_completer != null) _completer.complete(v);
-    _completer = new Completer();
-    return _completer.future;
-  }
-
-  // Release whoever is currently waiting.
-  void release([v]) {
-    if (_completer != null) {
-      _completer.complete(v);
-      _completer = null;
-    }
-  }
-}