anchor.diff:    runApp(new MaterialApp(
       title: 'Usage Example',
       theme: new ThemeData.dark(),
  -    routes: <String, RouteBuilder>{
  -      '/': (RouteArguments args) => new FlutterDemo(ga)
  +    routes: <String, WidgetBuilder>{
  +      '/': (BuildContext context) => new FlutterDemo(ga)
       }
     ));
   }
   
  -class FlutterDemo extends StatefulComponent {
  +class FlutterDemo extends StatefulWidget {
     FlutterDemo(this.ga);
     Analytics ga;
     State createState() => new _FlutterDemoState();
  
positive.code:           ),
            new ListItem(
              onTap: () => _handleOptIn(!config.ga.optIn),
              left: new Checkbox(
                value: config.ga.optIn,
                onChanged: _handleOptIn
              ),
              primary: new Text("Opt in to analytics")
            )
          ],
          justifyContent: FlexJustifyContent.spaceAround
        ),
        floatingActionButton: new FloatingActionButton(
          child: new Icon(icon: Icons.add),
  
negative.code: 
    Widget build(BuildContext context) {
      return new Scaffold(
        appBar: new AppBar(
          title: new Text('Usage Example')
        ),
        body: new Column(
          children: <Widget>[
  