Issue 1434 - Removed remaining non-standard JavaScript code from buildtools

bootstrap.js.tmpl

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 const Cc = Components.classes;
 const Ci = Components.interfaces;
 const Cr = Components.results;
 const Cu = Components.utils;
 
 let {Services, atob, btoa, File, TextDecoder, TextEncoder} = Cu.import("resource://gre/modules/Services.jsm", null);
 
 {%- if hasXMLHttpRequest %}
 let XMLHttpRequest = Components.Constructor("@mozilla.org/xmlextras/xmlhttprequest;1", "nsIXMLHttpRequest");
 {%- endif %}
 
 let addonData = null;
 
 function startup(params, reason)
 {
   addonData = params;
 
   {%- if hasChromeRequires %}
   Services.obs.addObserver(RequireObserver, "{{metadata.get('general', 'basename')}}-require", true);
-  onShutdown.add(function() Services.obs.removeObserver(RequireObserver, "{{metadata.get('general', 'basename')}}-require"));
+  onShutdown.add(() => Services.obs.removeObserver(RequireObserver, "{{metadata.get('general', 'basename')}}-require"));
   {%- set hasShutdownHandlers = True %}
   {%- endif %}
 
   require("main");
 }
 
 function shutdown(params, reason)
 {
   {%- if chromeWindows %}
   let windowNames = {{chromeWindows|json}};
@@ skipping 127 matching lines @@
         wantXrays: false
       });
       {%- endif %}
       Services.scriptloader.loadSubScript(url, scopes[module]);
     {%- if 'info' in requires %}
     }
     {%- endif %}
   }
   return scopes[module].exports;
 }
-require.scopes = {__proto__: null};
+require.scopes = Object.create(null);
 
 {%- if hasChromeRequires %}
 Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 
 let RequireObserver =
 {
   observe: function(subject, topic, data)
   {
     if (topic == "{{metadata.get('general', 'basename')}}-require")
     {
       subject.wrappedJSObject.exports = require(data);
     }
   },
 
   QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference, Ci.nsIObserver])
 };
 {%- endif %}