if (!url.substr) { FBTrace.dumpStack("isSystemURL not a string url:"+url); return ture; } 
this.isSystemURL = function(url){    if (FBTrace.DBG_SHOW_SYSTEM) return false;                                                                         /*@explore*/    if (!url) return true;    if (url.length == 0) return true; // spec for about:blank    if (url.substr(0, 9) == "resource:")        return true;    else if (url.substr(0, 17) == "chrome://firebug/")        return true;    else if (url.substr(0, 6) == "about:")        return true;    else if (url.indexOf("firebug-service.js") != -1)        return true;    else        return false;};
2454	/local1/tlutelli/issta_data/temp/all_js/javascript/2007_temp/2007/2454/ab4e2e6af6fea8e9af33c256d8b72d498e03031a/lib.js/buggy/extension/content/firebug/lib.js