rem:  switch(contentType) { case "text/html": case "text/xul": case "text/rdf": case "text/xml": case "text/css": case "image/gif": case "image/jpeg": case "image/png": case "text/plain": case "application/http-index-format": 
add: try { var catMgr = Components.classes["@mozilla.org/categorymanager;1"] .getService(Components.interfaces.nsICategoryManager); var entry = catMgr.getCategoryEntry("Gecko-Content-Viewers", contentType); if (entry) { 
context:     isPreferred: function(contentType, desiredContentType)    {        // seems like we should be getting this from helper apps or something        switch(contentType) {            case "text/html":            case "text/xul":            case "text/rdf":            case "text/xml":            case "text/css":            case "image/gif":            case "image/jpeg":            case "image/png":            case "text/plain":            case "application/http-index-format":                return true;        }        return false;    },
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/614a90cc82eb39026c50a183df86710a34b50c68/nsBrowserContentListener.js/buggy/xpfe/browser/resources/content/nsBrowserContentListener.js