Make new StreamController be async by default.

sdk/lib/io/directory_impl.dart

 // Copyright (c) 2012, 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.
 
 part of dart.io;
 
 class _Directory implements Directory {
   static const CREATE_REQUEST = 0;
   static const DELETE_REQUEST = 1;
   static const EXISTS_REQUEST = 2;
@@ skipping 229 matching lines @@
     const int LIST_DIRECTORY = 1;
     const int LIST_LINK = 2;
     const int LIST_ERROR = 3;
     const int LIST_DONE = 4;
 
     const int RESPONSE_TYPE = 0;
     const int RESPONSE_PATH = 1;
     const int RESPONSE_COMPLETE = 1;
     const int RESPONSE_ERROR = 2;
 
-    var controller = new StreamController<FileSystemEntity>();
+    var controller = new StreamController<FileSystemEntity>(sync: true);
 
     List request = [ _Directory.LIST_REQUEST, path, recursive, followLinks ];
     ReceivePort responsePort = new ReceivePort();
     // Use a separate directory service port for each listing as
     // listing operations on the same directory can run in parallel.
     _Directory._newServicePort().send(request, responsePort.toSendPort());
     responsePort.receive((message, replyTo) {
       if (message is !List || message[RESPONSE_TYPE] is !int) {
         responsePort.close();
         controller.addError(new DirectoryIOException("Internal error"));
@@ skipping 70 matching lines @@
 
   void _ensureDirectoryService() {
     if (_directoryService == null) {
       _directoryService = _newServicePort();
     }
   }
 
   final String _path;
   SendPort _directoryService;
 }