Convenience method for setting the status icon directly.  For more flexible options see {@link #setStatus}.
See {@link #iconCls} for complete details about customizing the icon.
@param {String} iconCls (optional) The icon class to set (defaults to '', and any current icon class is removed)
@return {Ext.ux.statusbar.StatusBar} this
function(cls) {
        var me = this;

        me.activeThreadId++;
        cls = cls || '';

        if (me.rendered) {
            if (me.currIconCls) {
                me.statusEl.removeCls(me.currIconCls);
                me.currIconCls = null;
            }
            if (cls.length > 0) {
                me.statusEl.addCls(cls);
                me.currIconCls = cls;
            }
        } else {
            me.currIconCls = cls;
        }
        return me;
    }