cachedIcon: function(src) {
        src = src.replace(/[&#]-moz-resolution=\d+,\d+$/, ""); // Firefox 22.0a1
        if(
            !/^https?:/.test(src)
            // IDN, see https://bugzilla.mozilla.org/show_bug.cgi?id=311045
            || /^https?:\/\/[^.:\/]+\.[^a-z0-9-]+(?:\/|$)/.test(src)
            || this.appName == "SeaMonkey" && this.appVersion <= 2
            || this.appName == "Firefox"   && this.appVersion <= 3.5
        )
            return src;
        return "moz-anno:favicon:" + src; // https://bugzilla.mozilla.org/show_bug.cgi?id=467828
    },

cachedIcon: function(src) {
        return src; // Always bypass cache
        src = src.replace(/[&#]-moz-resolution=\d+,\d+$/, ""); // Firefox 22.0a1
        if(
            !/^https?:/.test(src)
            // IDN, see https://bugzilla.mozilla.org/show_bug.cgi?id=311045
            || /^https?:\/\/[^.:\/]+\.[^a-z0-9-]+(?:\/|$)/.test(src)
            || this.appName == "SeaMonkey" && this.appVersion <= 2
            || this.appName == "Firefox"   && this.appVersion <= 3.5
        )
            return src;
        return "moz-anno:favicon:" + src; // https://bugzilla.mozilla.org/show_bug.cgi?id=467828
    },

properties: function(mi) {
        ...
                }\n\
                init();\n'
        + (this.before57 ? "" : '\
                window.onpageshow = () => {\n\
                    var callback = () => bookmarks.persist(document);\n\
                    var mo = new MutationObserver(callback);\n\
                    mo.observe(document.documentElement, {\n\
                        attributes: true, attributeFilter: ["screenX", "screenY", "width", "height"]\n\
                    });\n\
                    window.addEventListener("unload", () => {\n\
                        callback();\n\
                        mo.disconnect();\n\
                    }, {once: true});\n\
                }\n\
                window.opener.URL.revokeObjectURL(window.location.href);\n'
        ) + '\
                ]]></script>\n\
            </dialog>';

        /*
        window.openDialog(
            "data:application/vnd.mozilla.xul+xml," + encodeURIComponent(dialog.replace(/^\s+/, "")),
            "_blank",
            "chrome,all,resizable,centerscreen,dependent",
            mi, this, _localize
        );
        */
        dialog = dialog.replace(/^\s+/, "");
        if(this.before57)
            var url = "data:application/vnd.mozilla.xul+xml," + encodeURIComponent(dialog);
        else {
            var url = URL.createObjectURL(new Blob([dialog], {type: "application/vnd.mozilla.xul+xml"}));
            if(Services.prefs.prefHasUserValue(this.pref)) {
                var id = this.button.id + "-propertiesDialog";
                var attrs = JSON.parse(Services.prefs.getCharPref(this.pref));
                for(var attr in attrs) {
                    this.xs.setValue(url, id, attr, attrs[attr]);
                }
            }
        }
        window.openDialog(url, "_blank", "chrome,all,resizable,centerscreen,dependent", mi, this, _localize);
    },
    get before57() {
        var yes = this.appVersion < 57;
        if(!yes) {
            var pref = this.pref = "extensions." + this.button.id + ".propertiesDialog";
            addDestructor(function(reason) {
                if(reason == "delete")
                    Services.prefs.clearUserPref(pref);
            });
            this.xs = Components.classes["@mozilla.org/xul/xulstore;1"]
                .getService(Components.interfaces.nsIXULStore);
            this.persist = function(doc) {
                var url = doc.location.href;
                var dialog = doc.documentElement, id = dialog.id;

                var obj = {};
                ["screenX", "screenY", "width", "height"].forEach(function(attr) {
                    if(dialog.hasAttribute(attr))
                        obj[attr] = dialog.getAttribute(attr);
                });
                Services.prefs.setCharPref(pref, JSON.stringify(obj));

                var en = this.xs.getAttributeEnumerator(url, id);
                while(en.hasMore()) {
                    this.xs.removeValue(url, id, en.getNext());
                }
            }
        }
        delete this.before57;
        return this.before57 = yes;
    },