cocos creator 2.4.0兼容问题

fgui.addLoadHandler = function (ext) {

        var _a, _b;

        if (_flag)

            return;

        _flag = true;

        if (!ext)

            ext = "bin";

        

        cc.loader.addDownloadHandlers((_a = {}, _a[ext] = cc.loader.downloader["extMap"].binary, _a));

        cc.loader.addLoadHandlers((_b = {},

            _b[ext] = function (item, callback) {

                item._owner.rawBuffer = item.content;

                return item.content;

            },

            _b));

    };