Issue 6030 - Ensure RTCPeerConnection exists before wrapping it

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 207 matching lines @@
 
   /*
    * RTCPeerConnection wrapper
    *
    * The webRequest API in Chrome does not yet allow the blocking of
    * WebRTC connections.
    * See https://bugs.chromium.org/p/chromium/issues/detail?id=707683
    */
   let RealRTCPeerConnection = window.RTCPeerConnection ||
                                 window.webkitRTCPeerConnection;
+
+  // Firefox has the option (media.peerconnection.enabled) to disable WebRTC

[Manish Jethani, 2017/11/14 10:57:56]

Wouldn't it be better to wrap the entire code for RTCPeerConnection here into
the if block?

[Wladimir Palant, 2017/11/14 11:12:49]

I agree. While I'm normally not a big fan of increasing indentation level,
returning here might skip unrelated code that some future change adds below.

[kzar, 2017/11/14 11:36:35]

Done.

+  // in which case RealRTCPeerConnection is undefined. Note: This logic assumes
+  // that the WebRTC wrapping code comes last in the injected function!
+  if (typeof RealRTCPeerConnection == "undefined")
+    return;
+
   let closeRTCPeerConnection = Function.prototype.call.bind(
     RealRTCPeerConnection.prototype.close
   );
   let RealArray = Array;
   let RealString = String;
   let {create: createObject, defineProperty} = Object;
 
   function normalizeUrl(url)
   {
     if (typeof url != "undefined")
@@ skipping 158 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);
   }
 }