code: function() {
      this._unsetLastRow();
      var elTr = this.getLastTrEl();
      if(elTr) {
          // Assign class
          Dom.addClass(elTr, DT.CLASS_LAST);
          this._sLastTrId = elTr.id;
      }
  }
docs: Assigns the class YAHOO.widget.DataTable.CLASS_LAST to the last TR element
  of the DataTable page and updates internal tracker.
  
  @method _setLastRow
  @private