code: function() {
          var me = this,
              idx;
              
          if ((idx = Ext.Array.indexOf(me.indexes, me.currentIndex)) !== -1) {
              me.currentIndex = me.indexes[idx - 1] || me.indexes[me.indexes.length - 1];
              me.getSelectionModel().select(me.currentIndex);
           }
      }
docs: Selects the previous row containing a match.
  @private