Issue 5750 - Remove ext_background requires needed for legacy Gecko

lib/antiadblockInit.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/>.
  */
 
 "use strict";
 
 const {Prefs} = require("prefs");
 const {ActiveFilter} = require("filterClasses");
 const {FilterStorage} = require("filterStorage");
 const {FilterNotifier} = require("filterNotifier");
 const {Subscription} = require("subscriptionClasses");
 const {Notification} = require("notification");
 
-let ext;
-if (typeof window != "undefined" && window.ext)
-  ({ext} = window);
-else
-  ext = require("ext_background");
-
 exports.initAntiAdblockNotification = function initAntiAdblockNotification()
 {
   let notification = {
     id: "antiadblock",
     type: "question",
     title: ext.i18n.getMessage("notification_antiadblock_title"),
     message: ext.i18n.getMessage("notification_antiadblock_message"),
     urlFilters: []
   };
 
@@ skipping 46 matching lines @@
     if (url in FilterStorage.knownSubscriptions && subscription.disabled)
       addAntiAdblockNotification(subscription);
     else
       removeAntiAdblockNotification();
   }
 
   FilterNotifier.on("subscription.updated", onSubscriptionChange);
   FilterNotifier.on("subscription.removed", onSubscriptionChange);
   FilterNotifier.on("subscription.disabled", onSubscriptionChange);
 };