fix analyzer issue in listorder_test

samples/third_party/todomvc/test/listorder_test.dart

 // Copyright (c) 2013, 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.
 
 library todomvc.test.listorder_test;
 
 import 'dart:html';
 import 'package:polymer/polymer.dart';
+import 'package:polymer/platform.dart' show endOfMicrotask;
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 import '../web/model.dart';
 
 /**
  * This test runs the TodoMVC app, adds a few elements, marks some as done, and
  * switches from back and forth between "Active" and "All". This will make some
  * nodes to be hidden and readded to the page.
  */
 @initMethod
 _main() {
   useHtmlConfiguration();
 
-
   ShadowRoot root;
 
   setUp(() => Polymer.onReady.then((_) {
     root = query('todo-app').shadowRoot;
   }));
 
   test('programmatically add items to model', () {
     appModel.todos.addAll([
       new Todo('one (unchecked)'),
       new Todo('two (checked)')..done = true,
@@ skipping 25 matching lines @@
     }));
   });
 
   test('navigate back to #/', () {
     windowLocation.hash = '#/';
     endOfMicrotask(expectAsync0(() {
       expect(root.queryAll('#todo-list li[is=todo-row]').length, 3);
     }));
   });
 }