Aborts an active request.
@param {Object} [request] Defaults to the last request
function(request) {
        var me = this,
            xhr;
        
        if (!request) {
            request = me.getLatest();
        }

        if (request && me.isLoading(request)) {
            /*
             * Clear out the onreadystatechange here, this allows us
             * greater control, the browser may/may not fire the function
             * depending on a series of conditions.
             */
            xhr = request.xhr;
            try {
                xhr.onreadystatechange = null;
            } catch (e) {
                // Setting onreadystatechange to null can cause problems in IE, see
                // http://www.quirksmode.org/blog/archives/2005/09/xmlhttp_notes_a_1.html
                xhr.onreadystatechange = Ext.emptyFn;
            }
            xhr.abort();
            me.clearTimeout(request);
            if (!request.timedout) {
                request.aborted = true;
            }
            me.onComplete(request);
            me.cleanup(request);
        }
    }