rem: return Components.classes["@mozilla.org/file/directory_service;1"]. getService(Components.interfaces.nsIProperties). get(aKey, nsIFile); 
add: try { return Components.classes["@mozilla.org/file/directory_service;1"]. getService(Components.interfaces.nsIProperties). get(aKey, nsIFile); } catch (e) { throw "Couln't get directory service key: " + aKey; } 
context: function getDirectoryKey(aKey) {  return Components.classes["@mozilla.org/file/directory_service;1"].    getService(Components.interfaces.nsIProperties).    get(aKey, nsIFile);}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/73413ab825973044e43a9ecb941b3c58dda5f311/nsXULAppInstall.js/clean/xulrunner/setup/nsXULAppInstall.js