code: function softwareUpdate() {
    this._controller = null;
    this._wizard = null;
  
    this._aus = Cc["@mozilla.org/updates/update-service;1"].
                getService(Ci.nsIApplicationUpdateService);
    this._ums = Cc["@mozilla.org/updates/update-manager;1"].
                getService(Ci.nsIUpdateManager);
    this._vc = Cc["@mozilla.org/xpcom/version-comparator;1"].
               getService(Ci.nsIVersionComparator);
  }
docs: Constructor for software update class