Quick-restarts Firefox.

restart.ubiq.js

CmdUtils.CreateCommand({
  name: 'restart',
  icon: 'chrome://ubiquity/skin/icons/arrow_redo.png',
  description:
  (''+<>Restarts Firefox quickly.
   ( based on <a href="chrome://mozapps/content/extensions/extensions.js"
     >restartApp</a>)</>),
  execute: function(){
    const os = (Cc['@mozilla.org/observer-service;1']
                .getService(Ci.nsIObserverService));
    const cancelQuit = (Cc['@mozilla.org/supports-PRBool;1']
                        .createInstance(Ci.nsISupportsPRBool));
    os.notifyObservers(cancelQuit, 'quit-application-requested', 'restart');
    if(cancelQuit.data) return displayMessage({
      icon: this.icon, title: this.name,
      text: 'Something aborted the quit process',
    });
    const {nsIAppStartup} = Ci;
    Cc['@mozilla.org/toolkit/app-startup;1'].getService(nsIAppStartup)
      .quit(nsIAppStartup.eRestart | nsIAppStartup.eAttemptQuit);
  },
  author: 'satyr'.link('http://d.hatena.ne.jp/murky-satyr'),
  license: 'MIT',
});