Issue 4580 - Replace ext.backgroundPage.sendMessage with runtime.sendMessage

subscriptionLink.postload.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 75 matching lines @@
     // Default title to the URL
     if (!title)
       title = url;
 
     // Trim spaces in title and URL
     title = title.trim();
     url = url.trim();
     if (!/^(https?|ftp):/.test(url))
       return;
 
-    ext.backgroundPage.sendMessage({
+    chrome.runtime.sendMessage({
       type: "subscriptions.add",
       title,
       url,
       confirm: true
     });
   }, true);
 }