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: const Duration _kDropDownMenuDuration = const Duration(milliseconds: 300);
  const double _kMenuItemHeight = 48.0;
  const EdgeInsets _kMenuVerticalPadding = const EdgeInsets.symmetric(vertical: 8.0);
  const EdgeInsets _kMenuHorizontalPadding = const EdgeInsets.symmetric(horizontal: 36.0);
  const double _kBaselineOffsetFromBottom = 20.0;
  const double _kBottomBorderHeight = 2.0;
  const Border _kDropDownUnderline = const Border(bottom: const BorderSide(color: const Color(0xFFBDBDBD), width: _kBottomBorderHeight));
  
negative.code: }
  
  class _DropDownButtonState<T> extends State<DropDownButton<T>> {
    @override
    void initState() {
      super.initState();
  