Avoid double-// on directory listing.

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 309 matching lines @@
   int id;
   bool canceled = false;
   bool nextRunning = false;
   bool closed = false;
 
   _AsyncDirectoryLister(String this.path,
                         bool this.recursive,
                         bool this.followLinks) {
     controller = new StreamController(onListen: onListen,
                                       onResume: onResume,
-                                      onCancel: onCancel);
+                                      onCancel: onCancel,
+                                      sync: true);
   }
 
   Stream get stream => controller.stream;
 
   void onListen() {
     var request = [_Directory.LIST_START_REQUEST, path, recursive, followLinks];
     _Directory._newServicePort().call(request)
         .then((response) {
           if (response is int) {
             id = response;
@@ skipping 83 matching lines @@
       controller.addError(
           new DirectoryException("Directory listing failed",
                                  errorPath,
                                  err));
     } else {
       controller.addError(
           new DirectoryException("Internal error"));
     }
   }
 }