Issue 2259 - Removed non-standard JavaScript code from Element Hiding Helper

lib/main.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 Cu.import("resource://gre/modules/Services.jsm");
 
 let {Prefs} = require("prefs");
 let {WindowObserver} = require("windowObserver");
 let {WindowWrapper} = require("windowWrapper");
 
 // Check whether some preferences can still be found under their old locations
 Prefs.migrate("extensions.adblockplus.ehh-selectelement_key", "selectelement_key");
 Prefs.migrate("extensions.adblockplus.ehh.showhelp", "showhelp");
 
 // Window types to attach to
-let knownWindowTypes =
-{
-  "navigator:browser": true,
-  "mail:3pane": true,
-  "mail:messageWindow": true,
-  __proto__: null
-};
+let knownWindowTypes = new Set(["navigator:browser", "mail:3pane", "mail:messageWindow"]);
 
 // Use random marker class
 let elementMarkerClass = null;
 {
   let rnd = [];
   let offset = "a".charCodeAt(0);
   for (let i = 0; i < 20; i++)
     rnd.push(offset + Math.random() * 26);
 
   elementMarkerClass = String.fromCharCode.apply(String, rnd);
 }
 exports.elementMarkerClass = elementMarkerClass;
 
 // Load CSS asynchronously
 let request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIXMLHttpRequest);
 request.open("GET", "chrome://elemhidehelper/content/elementmarker.css");
 request.overrideMimeType("text/plain");
 request.addEventListener("load", function(event)
 {
   if (onShutdown.done)
     return;
 
   let data = event.target.responseText.replace(/%%CLASS%%/g, elementMarkerClass);
   let styleService = Cc["@mozilla.org/content/style-sheet-service;1"].getService(Ci.nsIStyleSheetService);
   let styleURI = Services.io.newURI("data:text/css," + encodeURIComponent(data), null, null);
   styleService.loadAndRegisterSheet(styleURI, Ci.nsIStyleSheetService.USER_SHEET);
-  onShutdown.add(function() styleService.unregisterSheet(styleURI, Ci.nsIStyleSheetService.USER_SHEET));
+  onShutdown.add(() => styleService.unregisterSheet(styleURI, Ci.nsIStyleSheetService.USER_SHEET));
 }, false);
 request.send(null);
 
 // Load overlay asynchonously and start attaching to windows once done
 request = Cc["@mozilla.org/xmlextras/xmlhttprequest;1"].createInstance(Ci.nsIJSXMLHttpRequest);
 request.open("GET", "chrome://elemhidehelper/content/overlay.xul");
 request.addEventListener("load", function(event)
 {
   if (onShutdown.done)
     return;
 
   let overlay = event.target.responseXML.documentElement;
 
   // Initialization done, we can start up now
   require("inspectorObserver");
   new WindowObserver({
     applyToWindow: function(window)
     {
       let type = window.document.documentElement.getAttribute("windowtype");
-      if (!(type in knownWindowTypes) || window._ehhWrapper)
+      if (!knownWindowTypes.has(type) || window._ehhWrapper)
         return;
 
       window.document.documentElement.appendChild(overlay.cloneNode(true));
 
       let style = window.document.createProcessingInstruction("xml-stylesheet", 'class="elemhidehelper-node" href="chrome://elemhidehelper/skin/overlay.css" type="text/css"');
       window.document.insertBefore(style, window.document.firstChild);
 
       window._ehhWrapper = new WindowWrapper(window);
     },
 
     removeFromWindow: function(window)
     {
       if (!window._ehhWrapper)
         return;
 
       window._ehhWrapper.shutdown();
       delete window._ehhWrapper;
 
       let element = window.document.getElementById(overlay.getAttribute("id"));
       if (element)
         element.parentNode.removeChild(element);
 
       for (let child = window.document.firstChild; child; child = child.nextSibling)
         if (child.nodeType == child.PROCESSING_INSTRUCTION_NODE && child.data.indexOf("elemhidehelper-node") >= 0)
           child.parentNode.removeChild(child);
     }
   });
 }, false);
 request.send(null);