Issue 5650 - Prevent attachShadowRoot to create closed shadow root.

inject.preload.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 125 matching lines @@
       });
     }
   }
 
   /*
    * Closed shadowRoot prevention.
    * https://issues.adblockplus.org/ticket/5650
    */
   if ("attachShadow" in Element.prototype)
   {
-    Element.prototype._attachShadow = Element.prototype.attachShadow;
-    Element.prototype.attachShadow = options => {
-      if (options && options.mode == "closed") {
+    let _attachShadow = Element.prototype.attachShadow;
+    Element.prototype.attachShadow = options =>
+    {
+      if (options && options.mode == "closed")
         options.mode = "open";
-      }
-      return this._attachShadow(options);
+
+      return _attachShadow.call(this, options);

[lainverse, 2017/10/02 06:41:21]

Arrow functions doesn't have their own 'this' and 'arguments'.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Functions/A...

     };
   }
 
   /*
    * Shared request checking code, used by both the WebSocket and
    * RTCPeerConnection wrappers.
    */
   let RealCustomEvent = window.CustomEvent;
 
   // If we've been injected into a frame via contentWindow then we can simply
@@ skipping 249 matching lines @@
   if (typeof sandbox != "string" || /(^|\s)allow-scripts(\s|$)/i.test(sandbox))
   {
     let script = document.createElement("script");
     script.type = "application/javascript";
     script.async = false;
     script.textContent = "(" + injected + ")('" + randomEventName + "');";
     document.documentElement.appendChild(script);
     document.documentElement.removeChild(script);
   }
 }