Turn on Polymer TodoMVC tests on Dart buildbots

samples/third_party/todomvc/test/mainpage_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.mainpage_test;
+
+import 'dart:async';
+import 'dart:html';
+import 'package:polymer/polymer.dart';
+import 'package:unittest/unittest.dart';
+import 'package:unittest/html_config.dart';
+import '../web/app.dart';
+import '../web/model.dart';
+
+/**
+ * This test runs the TodoMVC app and checks the state of the initial page.
+ */
+// TODO(jmesserly): verify some styles (colors, fonts, relative size) as well.
+main() {
+  useHtmlConfiguration();
+
+  test('initial state', () {
+    final todoApp = query('todo-app');
+    expect(appModel.todos.length, 0);
+    expect(todoApp.xtag is TodoApp, true, reason: 'TodoApp should bee created');
+
+    final root = todoApp.shadowRoot;
+    final newTodo = root.query('#new-todo');
+    expect(newTodo.placeholder, "What needs to be done?");
+
+    // Wait for setTimeout 0 for focus to activate.
+    Timer.run(expectAsync0(() {
+      expect(document.activeElement, todoApp, reason: 'app should have focus');
+      expect(root.activeElement, newTodo, reason: 'New todo should have focus');
+      expect(root.queryAll('[is=todo-row]').length, 0, reason: 'no items yet');
+    }));
+  });
+}