anchor.diff:    TreeViewCell _currentDragOverCell;
     // Whether the user can drag a cell.
     bool draggingEnabled = false;
  +  // Timer to expand cell on dragover
  +  Timer _pendingExpansionTimer;
  +  // nodeUID associated with above timer
  +  String _pendingExpansionUID;
     // Unique identifier of the tree.
     String _uuid;
   
  
positive.code:       }
        if (cell != null) {
          cell.dragOverlayVisible = true;
     
          //expand cell if it's a pausing drag hover
          new Timer(const Duration(milliseconds: 1000), () {
            if(_currentDragOverCell != null) {
              if(nodeUID == _currentDragOverCell.nodeUID) {
                if(!isNodeExpanded(nodeUID)) {
  
negative.code:     _listView = new ListView(element, this);
      _rows = null;
      _rowsMap = null;
      _pendingExpansionTimer = null;
      _pendingExpansionUID = null;
      reloadData();
    }
  
  