The Tor Browser / file revision

 var gBasePath = "tests/dom/datastore/tests/";

 function handleRequest(request, response) {

   var query = getQuery(request);

   var testToken = '';

   if ('testToken' in query) {

     testToken = query.testToken;

   }

   var template = 'file_app.template.webapp';

   if ('template' in query) {

     template = query.template;

   }

   var template = gBasePath + template;

   response.setHeader("Content-Type", "application/x-web-app-manifest+json", false);

   response.write(readTemplate(template).replace(/TESTTOKEN/g, testToken));

 }

 // Copy-pasted incantations. There ought to be a better way to synchronously read

 // a file into a string, but I guess we're trying to discourage that.

 function readTemplate(path) {

   var file = Components.classes["@mozilla.org/file/directory_service;1"].

                         getService(Components.interfaces.nsIProperties).

                         get("CurWorkD", Components.interfaces.nsILocalFile);

   var fis  = Components.classes['@mozilla.org/network/file-input-stream;1'].

                         createInstance(Components.interfaces.nsIFileInputStream);

   var cis = Components.classes["@mozilla.org/intl/converter-input-stream;1"].

                        createInstance(Components.interfaces.nsIConverterInputStream);

   var split = path.split("/");

   for(var i = 0; i < split.length; ++i) {

     file.append(split[i]);

   }

   fis.init(file, -1, -1, false);

   cis.init(fis, "UTF-8", 0, 0);

   var data = "";

   let (str = {}) {

     let read = 0;

     do {

       read = cis.readString(0xffffffff, str); // read as much as we can and put it in str.value

       data += str.value;

     } while (read != 0);

   }

   cis.close();

   return data;

 }

 function getQuery(request) {

   var query = {};

   request.queryString.split('&').forEach(function (val) {

     var [name, value] = val.split('=');

     query[name] = unescape(value);

   });

   return query;

 }