Update dart:io tests to use asyncStart/asyncEnd

tests/standalone/io/file_system_links_test.dart

 // Copyright (c) 2013, 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.
 
+import "dart:io";
+
+import "package:async_helper/async_helper.dart";
 import "package:expect/expect.dart";
-import "dart:io";
-import "dart:isolate";
-
 
 createLink(String dst, String link, void callback()) {
   new Link(link).create(dst).then((_) => callback());
 }
 
 
 testFileExistsCreate() {
   var temp = new Directory('').createTempSync();
   var x = '${temp.path}${Platform.pathSeparator}x';
   var y = '${temp.path}${Platform.pathSeparator}y';
@@ skipping 127 matching lines @@
       Expect.isFalse(link.existsSync());
       Expect.isTrue(temp2.existsSync());
       Expect.isTrue(new File(x).existsSync());
       temp2.deleteSync(recursive: true);
     });
   });
 }
 
 
 testDirectoryListing() {
-  var keepAlive = new ReceivePort();
+  asyncStart();
   var temp = new Directory('').createTempSync();
   var temp2 = new Directory('').createTempSync();
   var y = '${temp.path}${Platform.pathSeparator}y';
   var x = '${temp2.path}${Platform.pathSeparator}x';
   new File(x).createSync();
   createLink(temp2.path, y, () {
     var files = [];
     var dirs = [];
     for (var entry in temp.listSync(recursive:true)) {
       if (entry is File) {
@@ skipping 19 matching lines @@
             dirs.add(entity.path);
           }
         },
         onDone: () {
           Expect.equals(1, files.length);
           Expect.isTrue(files[0].endsWith('$y${Platform.pathSeparator}x'));
           Expect.equals(1, dirs.length);
           Expect.isTrue(dirs[0].endsWith(y));
           temp.deleteSync(recursive: true);
           temp2.deleteSync(recursive: true);
-          keepAlive.close();
+          asyncEnd();
         });
   });
 }
 
 
 testDirectoryListingBrokenLink() {
-  var keepAlive = new ReceivePort();
+  asyncStart();
   var temp = new Directory('').createTempSync();
   var x = '${temp.path}${Platform.pathSeparator}x';
   var link = '${temp.path}${Platform.pathSeparator}link';
   var doesNotExist = 'this_thing_does_not_exist';
   new File(x).createSync();
   createLink(doesNotExist, link, () {
     temp.listSync(recursive: true);  // No exceptions.
     var files = [];
     var dirs = [];
     var links = [];
@@ skipping 11 matching lines @@
         },
         onError: (e) => errors.add(e),
         onDone: () {
           Expect.equals(1, files.length);
           Expect.isTrue(files[0].endsWith(x));
           Expect.equals(1, links.length);
           Expect.isTrue(links[0].endsWith(link));
           Expect.equals(0, dirs.length);
           Expect.equals(0, errors.length);
           temp.deleteSync(recursive: true);
-          keepAlive.close();
+          asyncEnd();
         });
   });
 }
 
 
 main() {
   // Links on Windows are tested by windows_file_system_[async_]links_test.
   if (Platform.operatingSystem != 'windows') {
     testFileExistsCreate();
     testFileDelete();
     testFileWriteRead();
     testDirectoryExistsCreate();
     testDirectoryDelete();
     testDirectoryListing();
     testDirectoryListingBrokenLink();
   }
 }