anchor.diff:      Widget result = new DefaultTextStyle(
         style: style,
         child: new Row(
  +        mainAxisAlignment: MainAxisAlignment.spaceBetween,
           mainAxisSize: MainAxisSize.min,
  -        mainAxisAlignment: MainAxisAlignment.spaceBetween,
           children: <Widget>[
             // We use an IndexedStack to make sure we have enough width to show any
             // possible item as the selected item without changing size.
             new IndexedStack(
  -            key: _itemKey,
               index: _selectedIndex,
               alignment: FractionalOffset.centerLeft,
               children: config.items
  
positive.code: }
  
  class _DropDownButtonState<T> extends State<DropDownButton<T>> {
    final GlobalKey _itemKey = new GlobalKey(debugLabel: 'DropDownButton item key');
  
    @override
    void initState() {
      super.initState();
  
negative.code: 
    void _handleTap() {
      assert(_currentRoute == null);
      final RenderBox itemBox = context.findRenderObject();
      final Rect itemRect = itemBox.localToGlobal(Point.origin) & itemBox.size;
      final Completer<_DropDownRouteResult<T>> completer = new Completer<_DropDownRouteResult<T>>();
      _currentRoute = new _DropDownRoute<T>(
  