rem: if (aCommand == "cmd_cleanUp") 
add: if (!window.gDownloadsView) return false;  switch (aCommand) { case "cmd_cleanup": 
context:   isCommandEnabled: function (aCommand)  {    if (aCommand == "cmd_cleanUp")       return gDownloadManager.canCleanUp;    return false;  },
meta: 10520	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/10520/a1584e4fdb4e43cf0a4e6b90d9625d12ca4aa99a/downloads.js/clean/toolkit/mozapps/downloads/content/downloads.js