後は何なりと
(function(){
const nsIAppStartup = Components.interfaces.nsIAppStartup;
var mediator = Components.classes["@mozilla.org/appshell/window-mediator;1"]
.getService(Components.interfaces.nsIWindowMediator);
var windowType = "navigator:browser";
var enumerator = mediator.getEnumerator(windowType);
var flg = false;
while(enumerator.hasMoreElements()) {
var win = enumerator.getNext();
if(window != win) flg = true;
}
if(flg){
window.close();
}
})();