Issue 4795 - Use modern JavaScript syntax

chrome/ext/content.js

 "use strict";
 
 chrome.runtime.onMessage.addListener((message, sender, sendResponse) =>
 {
   return ext.onMessage._dispatch(message, {}, sendResponse).indexOf(true) != -1;
 });
 
-ext.onExtensionUnloaded = (() =>
 {
   let port = null;
 
-  return {
+  ext.onExtensionUnloaded = {
     addListener(listener)
     {
       if (!port)
         port = chrome.runtime.connect();
 
       // When the extension is reloaded, disabled or uninstalled the
       // background page dies and automatically disconnects all ports
       port.onDisconnect.addListener(listener);
     },
     removeListener(listener)
     {
       if (port)
       {
         port.onDisconnect.removeListener(listener);
 
         if (!port.onDisconnect.hasListeners())
         {
           port.disconnect();
           port = null;
         }
       }
     }
   };
-})();
+}