anchor.diff:      _user = "Guest${new math.Random().nextInt(1000)}";
       _currentMessage = '';
       _firebase.onChildAdded.listen((Event event) {
  -      Map<String, String> message = event.snapshot.val();
  -      setState(() => _messages.add(message));
  +      setState(() => _messages.add(event.snapshot.val()));
       });
       _messages = <Map<String, String>>[];
       super.initState();
  
positive.code:             new Flexible(
                child: new Block(
                  scrollAnchor: ViewportAnchor.end,
                  children: new Iterable.generate(_messages.length)
                                        .map((index) => _buildMessage(index))
                                        .toList()
                )
              ),
              _buildTextComposer(),
  
negative.code:       'text': text,
      };
      _firebase.push().set(message);
    }
  
    GlobalKey _messageKey = new GlobalKey();
  