Issue 4795 - Use modern JavaScript syntax

lib/subscriptionInit.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 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/>.
  */
 
 /** @module subscriptionInit */
 
 "use strict";
 
-let {Subscription, DownloadableSubscription,
-     SpecialSubscription} = require("subscriptionClasses");
-let {FilterStorage} = require("filterStorage");
-let {FilterNotifier} = require("filterNotifier");
-let {Prefs} = require("prefs");
-let {Synchronizer} = require("synchronizer");
-let {Utils} = require("utils");
-let {initNotifications} = require("notificationHelper");
+const {Subscription, DownloadableSubscription,
+       SpecialSubscription} = require("subscriptionClasses");
+const {FilterStorage} = require("filterStorage");
+const {FilterNotifier} = require("filterNotifier");
+const {Prefs} = require("prefs");
+const {Synchronizer} = require("synchronizer");
+const {Utils} = require("utils");
+const {initNotifications} = require("notificationHelper");
 
 let firstRun;
 let subscriptionsCallback = null;
 
 /**
  * If there aren't any filters, the default subscriptions are added.
  * However, if patterns.ini already did exist and/or any preference
  * is set to a non-default value, this indicates that this isn't the
  * first run, but something went wrong.
  *
@@ skipping 133 matching lines @@
  */
 exports.reinitialized = false;
 
 /**
  * Sets a callback that is called with an array of subscriptions to be added
  * during initialization. The callback must return an array of subscriptions
  * that will effectively be added.
  *
  * @param {function}
  */
-exports.setSubscriptionsCallback = function(callback)
+exports.setSubscriptionsCallback = callback =>
 {
   subscriptionsCallback = callback;
 };