anchor.diff:        child: title ?? new Container()
       );
       Widget center = primaryLine;
  -    if (isTwoLine || isThreeLine) {
  +    if (subtitle != null && (isTwoLine || isThreeLine)) {
         center = new Column(
           mainAxisAlignment: MainAxisAlignment.collapse,
           crossAxisAlignment: CrossAxisAlignment.start,
  
positive.code:     else
        itemHeight = dense ? 76.0 : 88.0;
  
      double iconMarginTop = 0.0;
      if (isThreeLine)
        iconMarginTop = dense ? 8.0 : 16.0;
  
      // Overall, the list item is a Row() with these children.
      final List<Widget> children = <Widget>[];
  
      if (leading != null) {
        children.add(new Container(
          margin: new EdgeInsets.only(right: 16.0, top: iconMarginTop),
          width: 40.0,
          child: new Align(
            alignment: new FractionalOffset(0.0, isThreeLine ? 0.0 : 0.5),
            child: leading
          )
        ));
  
negative.code: 
      if (trailing != null) {
        children.add(new Container(
          margin: const EdgeInsets.only(left: 16.0),
          child: new Align(
            alignment: FractionalOffset.centerRight,
            child: trailing
          )
        ));
  