帮忙修复一下火狐这个UC基本！

// ==UserScript==
// @name               ScrollWithMouse.uc.js
// @namespace          ScrollWithMouse@gmail.com
// @description        免点击鼠标拖动，来自Mozest.com社区
// ==/UserScript==
(function() {
    var speed = 1;
    var scrollMode = 0;
    var scrollStartSWTM = -1;
    function mouseScroll(event) {
        if (scrollStartSWTM != -1) {
            var document = window.content.document;
            if (document.body instanceof HTMLFrameSetElement) {
                document = window.content.frames[0].document;
            }
            var factor = Math.max(document.body.scrollHeight, document.documentElement.scrollHeight) / window.content.innerHeight;
            var delta = speed * factor * (event.screenY - scrollStartSWTM);
            document.body.scrollTop += delta;
            document.documentElement.scrollTop += delta;
        }
        scrollStartSWTM = event.screenY;
    }
 
    function startScroll() {
        if (!scrollMode) {
            scrollMode = 1;
            window.addEventListener('mousemove', mouseScroll, true);
        }
    }
    function stopScroll() {
        if (scrollMode) {
            scrollMode = 0;
            scrollStartSWTM = -1;
            window.removeEventListener('mousemove', mouseScroll, true);
        }
    }
 
    var content = document.getElementById("content");
    content.addEventListener("mousemove",
    function(e) {
        if (e.clientX > window.content.document.documentElement.clientWidth) {
            startScroll();
        }
    },
    false);
    content.addEventListener("mouseout",
    function(e) {
        stopScroll();
    },
    false);
})();