Centralized event streams

runtime/observatory/tests/observatory_ui/nav/top-menu/element_test.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:unittest/unittest.dart';
 import 'package:observatory/src/elements/nav/menu.dart';
 import 'package:observatory/src/elements/nav/top_menu.dart';
 
 main() {
   NavTopMenuElement.tag.ensureRegistration();
 
-  final String tag = NavMenuElement.tag.name;
+  final tag = NavMenuElement.tag.name;
 
   group('instantiation', () {
     test('default', () {
-      final NavTopMenuElement e = new NavTopMenuElement();
+      final e = new NavTopMenuElement();
       expect(e, isNotNull, reason: 'element correctly created');
     });
     test('not last', () {
-      final NavTopMenuElement e = new NavTopMenuElement(last: false);
+      final e = new NavTopMenuElement(last: false);
       expect(e, isNotNull, reason: 'element correctly created');
       expect(e.last, isFalse, reason: 'element correctly created');
     });
     test('last', () {
-      final NavTopMenuElement e = new NavTopMenuElement(last: true);
+      final e = new NavTopMenuElement(last: true);
       expect(e, isNotNull, reason: 'element correctly created');
       expect(e.last, isTrue, reason: 'element correctly created');
     });
   });
   group('elements', () {
     test('created', () async {
-      final NavTopMenuElement e = new NavTopMenuElement();
+      final e = new NavTopMenuElement();
       document.body.append(e);
       await e.onRendered.first;
       expect(e.shadowRoot.children.length, isNonZero, reason: 'has elements');
       expect(e.shadowRoot.querySelector('content'), isNotNull,
                                                  reason: 'has content elements');
       e.remove();
       await e.onRendered.first;
       expect(e.shadowRoot.children.length, isZero, reason: 'is empty');
     });
     test('react to last change', () async {
-      final NavTopMenuElement e = new NavTopMenuElement(last: false);
+      final e = new NavTopMenuElement(last: false);
       document.body.append(e);
       await e.onRendered.first;
       expect((e.shadowRoot.querySelector(tag) as NavMenuElement).last, isFalse);
       e.last = true;
       await e.onRendered.first;
       expect((e.shadowRoot.querySelector(tag) as NavMenuElement).last, isTrue);
       e.last = false;
       await e.onRendered.first;
       expect((e.shadowRoot.querySelector(tag) as NavMenuElement).last, isFalse);
       e.remove();
       await e.onRendered.first;
     });
   });
 }