Re-implement directory polling.

pkg/watcher/test/no_subscription_test.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.
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:scheduled_test/scheduled_test.dart';
 import 'package:watcher/watcher.dart';
 
 import 'utils.dart';
 
 main() {
   initConfig();
 
   setUp(createSandbox);
 
   test('does not notify for changes when there were no subscribers', () {
     // Note that this test doesn't rely as heavily on the test functions in
     // utils.dart because it needs to be very explicit about when the event
     // stream is and is not subscribed.
     var watcher = createWatcher();
 
     // Subscribe to the events.
     var completer = new Completer();
-    var subscription = watcher.events.listen((event) {
+    var subscription = watcher.events.listen(wrapAsync((event) {
       expect(event.type, equals(ChangeType.ADD));
       expect(event.path, endsWith("file.txt"));
       completer.complete();
-    });
+    }));
 
     writeFile("file.txt");
 
     // Then wait until we get an event for it.
     schedule(() => completer.future);
 
     // Unsubscribe.
     schedule(() {
       subscription.cancel();
     });
 
     // Now write a file while we aren't listening.
     writeFile("unwatched.txt");
 
     // Then start listening again.
     schedule(() {
       completer = new Completer();
-      subscription = watcher.events.listen((event) {
+      subscription = watcher.events.listen(wrapAsync((event) {
         // We should get an event for the third file, not the one added while
         // we weren't subscribed.
         expect(event.type, equals(ChangeType.ADD));
         expect(event.path, endsWith("added.txt"));
         completer.complete();
-      });
+      }));
     });
 
     // The watcher will have been cancelled and then resumed in the middle of
     // its pause between polling loops. That means the second scan to skip
     // what changed while we were unsubscribed won't happen until after that
     // delay is done. Wait long enough for that to happen.
-    schedule(() => new Future.delayed(new Duration(seconds: 1)));
+    schedule(() => new Future.delayed(watcher.pollingDelay * 2));
 
     // And add a third file.
     writeFile("added.txt");
 
     // Wait until we get an event for the third file.
     schedule(() => completer.future);
 
     schedule(() {
       subscription.cancel();
     });
   });
 }