code: function(
      /*number*/ combinedWidth,
      /*number*/ leftOffset,
      /*number*/ cellWidth,
      /*?number*/ cellMinWidth,
      /*?number*/ cellMaxWidth,
      /*number|string*/ columnKey,
      /*object*/ event) {
      if (Locale.isRTL()) {
        leftOffset = -leftOffset;
      }
      this.setState({
        isColumnResizing: true,
        columnResizingData: {
          left: leftOffset + combinedWidth - cellWidth,
          width: cellWidth,
          minWidth: cellMinWidth,
          maxWidth: cellMaxWidth,
          initialEvent: {
            clientX: event.clientX,
            clientY: event.clientY,
            preventDefault: emptyFunction
          },
          key: columnKey
        }
      });
    }
docs: This is called when a cell that is in the header of a column has its
  resizer knob clicked on. It displays the resizer and puts in the correct
  location on the table.