rem: var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal); 
add: var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranch2); 
context: function addPrefListener(observer){  try {    var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal);    pbi.addObserver(observer.domain, observer, false);  } catch(ex) {    dump("Failed to observe prefs: " + ex + "\n");  }}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/48289f53e3b20b3f4fc4b90a9372f8a29b337b3a/navigator.js/buggy/suite/browser/navigator.js