Issue 4364 - Drop support for Chrome 29-40 and remove legacy code

composer.postload.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
@@ skipping 467 matching lines @@
   }
   unhighlightElements();
 
   let overlays = document.getElementsByClassName("__adblockplus__overlay");
   while (overlays.length > 0)
     overlays[0].parentNode.removeChild(overlays[0]);
 
   ext.onExtensionUnloaded.removeListener(deactivateBlockElement);
 }
 
-// In Chrome 37-40, the document_end content script (this one) runs properly,
-// while the document_start content scripts (that defines ext) might not. Check
-// whether variable ext exists before continuing to avoid
-// "Uncaught ReferenceError: ext is not defined". See https://crbug.com/416907
-if ("ext" in window && document instanceof HTMLDocument)
+if (document instanceof HTMLDocument)
 {
   // Use a contextmenu handler to save the last element the user right-clicked
   // on. To make things easier, we actually save the DOM event. We have to do
   // this because the contextMenu API only provides a URL, not the actual DOM
   // element.
   //   We also need to make sure that the previous right click event,
   // if there is one, is removed. We don't know which frame it is in so we must
   // send a message to the other frames to clear their old right click events.
   document.addEventListener("contextmenu", event =>
   {
@@ skipping 77 matching lines @@
             }
           });
         }
         break;
     }
   });
 
   if (window == window.top)
     ext.backgroundPage.sendMessage({type: "composer.ready"});
 }