Noissue - Fix some problems Firefox has with our injected code

inject.preload.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2017 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 156 matching lines @@
       dispatchEvent(new RealCustomEvent(eventName,
                                         {detail: {url, requestType}}));
     };
   }
 
   // Only to be called before the page's code, not hardened.
   function copyProperties(src, dest, properties)
   {
     for (let name of properties)
     {
-      Object.defineProperty(dest, name,
-                            Object.getOwnPropertyDescriptor(src, name));
+      let descriptor = Object.getOwnPropertyDescriptor(src, name);
+      if (descriptor)
+        Object.defineProperty(dest, name, descriptor);
     }
   }
 
   /*
    * WebSocket wrapper
    *
    * Required before Chrome 58, since the webRequest API didn't allow us to
    * intercept WebSockets.
    * See https://bugs.chromium.org/p/chromium/issues/detail?id=129353
    */
@@ skipping 162 matching lines @@
       realSetConfiguration(this, configuration);
       checkConfiguration(this, configuration);
     };
   }
 
   function WrappedRTCPeerConnection(...args)
   {
     if (!(this instanceof WrappedRTCPeerConnection))
       return WrappedRTCPeerConnection();
 
+
     let configuration = protectConfiguration(args[0]);
+
     // Since the old webkitRTCPeerConnection constructor takes an optional
     // second argument we need to take care to pass that through. Necessary
     // for older versions of Chrome such as 49.
-    let peerconnection = new RealRTCPeerConnection(configuration, args[1]);
+    let constraints = undefined;
+    if (args.length > 1)
+      constraints = args[1];
+
+    let peerconnection = new RealRTCPeerConnection(configuration, constraints);
     checkConfiguration(peerconnection, configuration);
     return peerconnection;
   }
 
   WrappedRTCPeerConnection.prototype = RealRTCPeerConnection.prototype;
 
   let boundWrappedRTCPeerConnection = WrappedRTCPeerConnection.bind();
   copyProperties(RealRTCPeerConnection, boundWrappedRTCPeerConnection,
                  ["caller", "generateCertificate", "name", "prototype"]);
   RealRTCPeerConnection.prototype.constructor = boundWrappedRTCPeerConnection;
 
   if ("RTCPeerConnection" in window)
     window.RTCPeerConnection = boundWrappedRTCPeerConnection;
   if ("webkitRTCPeerConnection" in window)
     window.webkitRTCPeerConnection = boundWrappedRTCPeerConnection;
 }
 
 if (document instanceof HTMLDocument)
 {
   let script = document.createElement("script");
   script.type = "application/javascript";
   script.async = false;
   script.textContent = "(" + injected + ")('" + randomEventName + "');";
   document.documentElement.appendChild(script);
   document.documentElement.removeChild(script);
 }