rem: obs.removeObserver(clearDownloadsObserver, "download-manager-clear-history"); 
add: obs.removeObserver(gDownloadObserver, "download-manager-remove-download"); 
context: function Shutdown() {  gDownloadManager.removeListener(gDownloadListener);  var obs = Components.classes["@mozilla.org/observer-service;1"].            getService(Components.interfaces.nsIObserverService);  obs.removeObserver(clearDownloadsObserver, "download-manager-clear-history");}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/10234/e20df2aa0991fedb2428568b2b1e88e9ff28e643/downloads.js/clean/toolkit/mozapps/downloads/content/downloads.js