Issue 5593 - Use messaging for the popup's notification code

notification.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
@@ skipping 97 matching lines @@
       {
         if (event.target.id == "notification-optout")
           setPref("notifications_ignoredcategories", true);
 
         notificationElement.hidden = true;
         notification.onClicked();
       }
     }, true);
   });
 }, false);