add:  var obs = Components.classes["@mozilla.org/observer-service;1"]. getService(Components.interfaces.nsIObserverService); obs.removeObserver(clearDownloadsObserver, "download-manager-clear-history"); 
context: function Shutdown() {  gDownloadManager.removeListener(gDownloadListener);}
meta: 8395	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/8395/58c7993d4e4725ed6694d7bfd453d72a9b5d9b1b/downloads.js/buggy/toolkit/mozapps/downloads/content/downloads.js