Centralized event streams

runtime/observatory/lib/src/elements/nav/notify.dart

 // Copyright (c) 2016, 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:html';
 import 'dart:async';
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/nav/notify_event.dart';
 import 'package:observatory/src/elements/nav/notify_exception.dart';
 
 class NavNotifyElement extends HtmlElement implements Renderable {
   static const tag = const Tag<NavNotifyElement>('nav-notify-wrapped',
           dependencies: const [ NavNotifyEventElement.tag,
                                 NavNotifyExceptionElement.tag ]);
 
   RenderingScheduler _r;
 
   Stream<RenderedEvent<NavNotifyElement>> get onRendered => _r.onRendered;
 
   M.NotificationRepository _repository;
   StreamSubscription _subscription;
 
   bool _notifyOnPause;
+
   bool get notifyOnPause => _notifyOnPause;
+  
   set notifyOnPause(bool value) =>
       _notifyOnPause = _r.checkAndReact(_notifyOnPause, value);
 
   factory NavNotifyElement(M.NotificationRepository repository,
                            {bool notifyOnPause: true, RenderingQueue queue}) {
     assert(repository != null);
     assert(notifyOnPause != null);
     NavNotifyElement e = document.createElement(tag.name);
     e._r = new RenderingScheduler(e, queue: queue);
     e._repository = repository;
     e._notifyOnPause = notifyOnPause;
     return e;
   }
 
   NavNotifyElement.created() : super.created();
 
   @override
   void attached() {
     super.attached();
+    _subscription = _repository.onChange.listen((_) => _r.dirty());
     _r.enable();
-    _subscription = _repository.onChange.listen((_) => _r.dirty());
   }
 
   @override
   void detached() {
     super.detached();
     children = [];
     _r.disable(notify: true);
     _subscription.cancel();
   }
 
@@ skipping 23 matching lines @@
       return new NavNotifyExceptionElement(
               notification.exception, stacktrace: notification.stacktrace,
               queue: _r.queue)
           ..onDelete.listen((_) => _repository.delete(notification));
     } else {
       assert(false);
       return new DivElement()..text = 'Invalid Notification Type';
     }
   }
 }