[Effen] Use the checkbox widget in the stocks app.

sky/examples/stocks/lib/stock_menu.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:sky/framework/fn.dart';
+import 'package:sky/framework/layout.dart';
 import 'package:sky/framework/components/popup_menu.dart';
-import 'package:sky/framework/fn.dart';
+import 'package:sky/framework/components/checkbox.dart';
 import 'package:sky/framework/theme/view_configuration.dart';
 
 class StockMenu extends Component {
   static final Style _style = new Style('''
     position: absolute;
     right: 8px;
     top: ${8 + kStatusBarHeight}px;''');
 
   PopupMenuController controller;
 
-  StockMenu({Object key, this.controller}) : super(key: key);
+  StockMenu({Object key, this.controller, this.autorefresh: false, this.onAutorefreshChanged}) : super(key: key);
+
+  final bool autorefresh;
+  final ValueChanged onAutorefreshChanged;
+
+  static FlexBoxParentData _flex1 = new FlexBoxParentData()..flex = 1;
 
   UINode build() {
+    var checkbox = new Checkbox(
+      checked: this.autorefresh,
+      onChanged: this.onAutorefreshChanged
+    );
+
     return new StyleNode(
       new PopupMenu(
         controller: controller,
         items: [
           [new Text('Add stock')],
           [new Text('Remove stock')],
-          [new Text('Help & feedback')],
+          [new ParentDataNode(new Text('Autorefresh'), _flex1), checkbox],
         ],
         level: 4),
         _style
     );
   }
 }