Issue 4406 - Treat about:srcdoc as not having an own security context, inherit document origin

lib/child/utils.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 83 matching lines @@
     frames.push(frame);
     window = (window != window.parent ? window.parent : null);
   }
 
   // URLs like about:blank inherit their security context from upper-level
   // frames, resolve their URLs accordingly.
   for (let i = frames.length - 2; i >= 0; i--)
   {
     let frame = frames[i];
     if (frame.location == "about:blank" || frame.location == "moz-safe-about:blank" ||
+        frame.location == "about:srcdoc" ||
         Utils.netUtils.URIChainHasFlags(Utils.makeURI(frame.location), Ci.nsIProtocolHandler.URI_INHERITS_SECURITY_CONTEXT))
     {
       frame.location = frames[i + 1].location;
     }
   }
 
   return frames;
 };
 
 /**
  * Checks whether Private Browsing mode is enabled for a content window.
  * @return {Boolean}
  */
 let isPrivate = exports.isPrivate = function(/**Window*/ window)
 {
   return PrivateBrowsingUtils.isContentWindowPrivate(window);
 };