Make the popup menu work again.

sky/examples/stocks2/lib/stock_settings.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/theme2/colors.dart' as colors;
 import 'package:sky/theme2/typography.dart' as typography;
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/checkbox.dart';
 import 'package:sky/widgets/icon_button.dart';
 import 'package:sky/widgets/menu_item.dart';
@@ skipping 23 matching lines @@
       backgroundColor: colors.Purple[500]
     );
   }
 
   Widget buildSettingsPane() {
     return new Container(
       padding: const EdgeDims.symmetric(vertical: 20.0),
       decoration: new BoxDecoration(backgroundColor: colors.Grey[50]),
       child: new Block([
         new MenuItem(
-          key: 'Optimistic Setting',
           icon: 'action/thumb_up',
           onGestureTap: (event) => _handleAwesomeChanged(!_awesome),
           children: [
             new Flexible(child: new Text('Everything is awesome')),
-            new Checkbox(key: 'awesome', value: _awesome, onChanged: _handleAwesomeChanged)
+            new Checkbox(value: _awesome, onChanged: _handleAwesomeChanged)
           ]
         ),
       ])
     );
   }
 
   Widget build() {
     return new Scaffold(
       toolbar: buildToolBar(),
       body: buildSettingsPane()
     );
   }
 }