Issue 5750 - Remove ext_background requires needed for legacy Gecko

messageResponder.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
 /* globals require */
 
 "use strict";
 
 (function(global)
 {
-  let ext = global.ext || require("ext_background");
-
   const {port} = require("messaging");
   const {Prefs} = require("prefs");
   const {Utils} = require("utils");
   const {FilterStorage} = require("filterStorage");
   const {FilterNotifier} = require("filterNotifier");
   const {defaultMatcher} = require("matcher");
   const {ElemHideEmulation} = require("elemHideEmulation");
   const {Notification: NotificationStorage} = require("notification");
 
   const {Filter, BlockingFilter, RegExpFilter} = require("filterClasses");
@@ skipping 389 matching lines @@
     if (message.url)
       subscriptions = [Subscription.fromURL(message.url)];
 
     for (let subscription of subscriptions)
     {
       if (subscription instanceof DownloadableSubscription)
         Synchronizer.execute(subscription, true);
     }
   });
 })(this);