Override to put the RTL class onto the innerCt so that columns can have a rule which switches float direction
function () {
        var renderData = this.callParent();

        if (this.owner.getHierarchyState().rtl) {
            renderData.innerCtCls =
                (renderData.innerCtCls || '') + ' ' + Ext.baseCSSPrefix + 'rtl';
        }
        
        return renderData;
    }