Make Sky example game run offline

sky/sdk/example/demo_launcher/lib/main.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 'dart:sky';
 
 import 'package:sky/mojo/activity.dart' as activity;
 import 'package:sky/mojo/asset_bundle.dart';
 import 'package:sky/mojo/shell.dart' as shell;
 import 'package:sky/painting/box_painter.dart';
@@ skipping 65 matching lines @@
     decoration: new BoxDecoration(
       backgroundImage: new BackgroundImage(
         image: _bundle.loadImage('assets/stocks_thumbnail.png'),
         fit: BackgroundFit.cover
       )
     )
   ),
   new SkyDemo(
     name: 'Asteroids',
     href: '../../game/main.dart',
+    bundle: 'game.skyx',
     description: '2D game using sprite sheets to achieve high performance',
     textTheme: typography.white,
     decoration: new BoxDecoration(
       backgroundImage: new BackgroundImage(
         image: _bundle.loadImage('assets/game_thumbnail.png'),
         fit: BackgroundFit.cover
       )
     )
   ),
   new SkyDemo(
@@ skipping 94 matching lines @@
           )
         )
       )
     );
   }
 }
 
 void main() {
   runApp(new SkyHome());
 }