Centralized event streams

runtime/observatory/lib/src/elements/nav/vm_menu_wrapper.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/app.dart';
-import 'package:observatory/mocks.dart';
-import 'package:observatory/models.dart' as M;
 import 'package:observatory/service.dart';
 import 'package:observatory/service_common.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/shims/binding.dart';
 import 'package:observatory/src/elements/nav/vm_menu.dart';
 
 @bindable
 class NavVMMenuElementWrapper extends HtmlElement {
   static const binder = const Binder<NavVMMenuElementWrapper>(const {
       'last': #last, 'vm': #vm
     });
 
   static const tag = const Tag<NavVMMenuElementWrapper>('vm-nav-menu');
 
-  StreamSubscription _subscription;
-  StreamController<M.VMUpdateEvent> _updatesController =
-      new StreamController<M.VMUpdateEvent>.broadcast();
-
   bool _last = false;
   VM _vm;
+
   bool get last => _last;
   VM get vm => _vm;
+
   set last(bool value) {
-    _last = value; render();
-  }
+    _last = value;
+    render(); }
   set vm(VM value) {
-    _vm = value; _detached(); _attached();
+    _vm = value;
+    render();
   }
 
   NavVMMenuElementWrapper.created() : super.created() {
     binder.registerCallback(this);
     _last = _getBoolAttribute('last');
     createShadowRoot();
     render();
   }
 
   @override
   void attached() {
     super.attached();
-    _attached();
-  }
-
-  @override
-  void detached() {
-    super.detached();
-    _detached();
-  }
-
-  void _attached() {
-    if (_vm != null) {
-      _subscription = _vm.changes.listen((_) {
-        _updatesController.add(new VMUpdateEventMock(vm: _vm));
-      });
-    }
     render();
   }
 
-  void _detached() {
-    if (_subscription != null) {
-      _subscription.cancel();
-      _subscription = null;
-    }
-  }
-
   void render() {
     shadowRoot.children = [];
-    if (_vm == null || _last == null) return;
+    if (_vm == null || _last == null) {
+      return;
+    }
 
     shadowRoot.children = [
-      new NavVMMenuElement(vm, _updatesController.stream, last: last,
-          target: (vm as CommonWebSocketVM)?.target,
-          queue: ObservatoryApplication.app.queue)
+      new NavVMMenuElement(vm, app.events, last: last,
+          queue: app.queue)
         ..children = [new ContentElement()]
     ];
   }
 
+  ObservatoryApplication get app => ObservatoryApplication.app;
+
   bool _getBoolAttribute(String name) {
     final String value = getAttribute(name);
     return !(value == null || value == 'false');
   }
 }