Centralized event streams

runtime/observatory/lib/src/elements/nav/library_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 'package:observatory/app.dart';
 import 'package:observatory/service.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 import 'package:observatory/src/elements/shims/binding.dart';
 import 'package:observatory/src/elements/nav/library_menu.dart';
 
 @bindable
 class NavLibraryMenuElementWrapper extends HtmlElement {
   static const binder = const Binder<NavLibraryMenuElementWrapper>(const {
       'last': #last, 'library': #library
     });
 
   static const tag =
     const Tag<NavLibraryMenuElementWrapper>('library-nav-menu');
 
   bool _last = false;
   Library _library;
+
   bool get last => _last;
   Library get library => _library;
+  
   set last(bool value) {
-    _last = value; render();
+    _last = value;
+    render();
   }
   set library(Library value) {
-    _library = value; render();
+    _library = value;
+    render();
   }
 
   NavLibraryMenuElementWrapper.created() : super.created() {
     binder.registerCallback(this);
     _last = _getBoolAttribute('last');
     createShadowRoot();
     render();
   }
 
   @override
   void attached() {
     super.attached();
     render();
   }
 
   void render() {
     shadowRoot.children = [];
-    if (_library == null || _last == null) return;
+    if (_library == null || _last == null) {
+      return;
+    }
 
     shadowRoot.children = [
       new NavLibraryMenuElement(library.isolate, library, last: last,
                                  queue: ObservatoryApplication.app.queue)
         ..children = [new ContentElement()]
     ];
   }
 
   bool _getBoolAttribute(String name) {
     final String value = getAttribute(name);
     return !(value == null || value == 'false');
   }
 }