const nsIAppStartup = Components.interfaces.nsIAppStartup;

    // Notify all windows that an application quit has been requested.
    var os = Components.classes["@mozilla.org/observer-service;1"]
        .getService(Components.interfaces.nsIObserverService);
    var cancelQuit = Components.classes["@mozilla.org/supports-PRBool;1"]
        .createInstance(Components.interfaces.nsISupportsPRBool);
    os.notifyObservers(cancelQuit, "quit-application-requested", null);

    // Something aborted the quit process. 
    if (cancelQuit.data)
        return;

    // Notify all windows that an application quit has been granted.
    os.notifyObservers(null, "quit-application-granted", null);

    // Enumerate all windows and call shutdown handlers
    var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"]
        .getService(Components.interfaces.nsIWindowMediator);
    var windows = wm.getEnumerator(null);
    while (windows.hasMoreElements()) {
        var win = windows.getNext();
        if (("tryToClose" in win) && !win.tryToClose())
            return;
    }
    Components.classes["@mozilla.org/toolkit/app-startup;1"].getService(nsIAppStartup)
        .quit(nsIAppStartup.eRestart | nsIAppStartup.eAttemptQuit);

This code works on FF 38 and earlier to for restarting, why not in 46? <pre><nowiki> const nsIAppStartup = Components.interfaces.nsIAppStartup; // Notify all windows that an application quit has been requested. var os = Components.classes["@mozilla.org/observer-service;1"] .getService(Components.interfaces.nsIObserverService); var cancelQuit = Components.classes["@mozilla.org/supports-PRBool;1"] .createInstance(Components.interfaces.nsISupportsPRBool); os.notifyObservers(cancelQuit, "quit-application-requested", null); // Something aborted the quit process. if (cancelQuit.data) return; // Notify all windows that an application quit has been granted. os.notifyObservers(null, "quit-application-granted", null); // Enumerate all windows and call shutdown handlers var wm = Components.classes["@mozilla.org/appshell/window-mediator;1"] .getService(Components.interfaces.nsIWindowMediator); var windows = wm.getEnumerator(null); while (windows.hasMoreElements()) { var win = windows.getNext(); if (("tryToClose" in win) && !win.tryToClose()) return; } Components.classes["@mozilla.org/toolkit/app-startup;1"].getService(nsIAppStartup) .quit(nsIAppStartup.eRestart | nsIAppStartup.eAttemptQuit);</nowiki></pre>