Issue 5028 - Use browser namespace

lib/filterComposer.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 200 matching lines @@
 {
   readyPages.set(sender.page, null);
   updateContextMenu(sender.page);
 });
 
 port.on("composer.openDialog", (message, sender) =>
 {
   return new Promise(resolve =>
   {
     ext.windows.create({
-      url: ext.getURL("composer.html"),
+      url: browser.extension.getURL("composer.html"),
       left: 50,
       top: 50,
       width: 420,
       height: 200,
       type: "popup"
     },
     popupPage =>
     {
       let popupPageId = popupPage.id;
       function onRemoved(removedPageId)
@@ skipping 31 matching lines @@
 
 port.on("composer.quoteCSS", (message, sender) =>
 {
   return quoteCSS(message.CSS);
 });
 
 ext.pages.onLoading.addListener(page =>
 {
   page.sendMessage({type: "composer.content.finished"});
 });