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: 5872	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/5872/361daac9367ad464688c4da3c3206d18cb2ae94e/navigator.js/clean/xpfe/browser/resources/content/navigator.js