rem: if (pbi) pbi.removeObserver(window.buttonPrefListener.domain, window.buttonPrefListener); 
add: pbi.removeObserver(window.buttonPrefListener.domain, window.buttonPrefListener); 
context: function Shutdown(){  // remove remote support  if (XREMOTESERVICE_CONTRACTID in Components.classes) {    var remoteService;    remoteService = Components.classes[XREMOTESERVICE_CONTRACTID]                              .getService(Components.interfaces.nsIXRemoteService);    remoteService.removeBrowserInstance(window);  }  var browser = getBrowser();  browser.boxObject.removeProperty("listenerkungfu");  try {    getBrowser().removeProgressListener(window.XULBrowserWindow);  } catch (ex) {  }  window.XULBrowserWindow.destroy();  window.XULBrowserWindow = null;  BrowserFlushBookmarksAndHistory();  // unregister us as a pref listener  var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal);  if (pbi)    pbi.removeObserver(window.buttonPrefListener.domain,                       window.buttonPrefListener);  window.browserContentListener.close();  // Close the app core.  if (appCore)    appCore.close();}
meta: 9421	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/9421/f0d6d8712b965f68658dd56fab062282d0ac6850/navigator.js/buggy/xpfe/browser/resources/content/navigator.js