rem: if (pbi) pbi.addObserver(this.domain, this, false); 
add: pbi.addObserver(this.domain, this, false); 
context: function nsButtonPrefListener(){  try {    var pbi = pref.QueryInterface(Components.interfaces.nsIPrefBranchInternal);    if (pbi)      pbi.addObserver(this.domain, this, false);  } catch(ex) {    dump("Failed to observe prefs: " + ex + "\n");  }}
meta: 8395	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/8395/f33cebfd69a5c5cfa7ad6446a366fc9098f15b8e/navigator.js/clean/xpfe/browser/resources/content/navigator.js