add:   var someHidden = this._defaultEngines.some(function (e) {return e.hidden;}); gEngineManagerDialog.showRestoreDefaults(someHidden); 
context: function EngineStore() {  var searchService = Cc["@mozilla.org/browser/search-service;1"].                      getService(Ci.nsIBrowserSearchService);  this._engines = searchService.getVisibleEngines({}).map(this._cloneEngine);  this._ops = [];}
meta: 10234	/local1/tlutelli/issta_data/temp/all_js/javascript/2006_temp/2006/10234/599cc60aa0b66effdc586d52ca8f8f2c2902b50f/engineManager.js/clean/browser/components/search/content/engineManager.js