Issue 1727 - Fix WebSocket constructor without second argument in Chrome 47

include.preload.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 361 matching lines @@
         new CustomEvent(eventName + "-" + event.detail.url, {detail: block})
       );
     });
   });
 
   runInDocument(document, function(eventName)
   {
     // As far as possible we must track everything we use that could be
     // sabotaged by the website later in order to circumvent us.
     var RealWebSocket = WebSocket;
-    var bindWebSocket = Function.prototype.bind.apply.bind(Function.prototype.bind, RealWebSocket);
     var closeWebSocket = Function.prototype.call.bind(RealWebSocket.prototype.close);
     var addEventListener = document.addEventListener.bind(document);
     var removeEventListener = document.removeEventListener.bind(document);
     var dispatchEvent = document.dispatchEvent.bind(document);
     var CustomEvent = window.CustomEvent;
 
     function checkRequest(url, callback)
     {
       var incomingEventName = eventName + "-" + url;
       function listener(event)
       {
         callback(event.detail);
         removeEventListener(incomingEventName, listener);
       }
       addEventListener(incomingEventName, listener);
 
       dispatchEvent(new CustomEvent(eventName, {
         detail: {url: url}
       }));
     }
 
-    WebSocket = function WrappedWebSocket()
-    {
-      var args = [this];
-      for (var i = 0; i < arguments.length; i++)
-        args[i + 1] = arguments[i];
-
-      var ctor = bindWebSocket(args);
-      var websocket = this instanceof WrappedWebSocket ? new ctor : ctor();
+    WebSocket = function WrappedWebSocket(url, protocols)
+    {
+      // Throw correct exceptions if the constructor is used improperly.
+      if (!(this instanceof WrappedWebSocket)) return RealWebSocket();
+      if (arguments.length < 1) return new RealWebSocket();
+
+      var websocket;
+      if (arguments.length == 1)
+        websocket = new RealWebSocket(url);
+      else
+        websocket = new RealWebSocket(url, protocols);

[Wladimir Palant, 2016/08/15 12:33:24]

Why make assumptions about the arguments in the first place? What if a third
parameter is added to the spec?

  var websocket = Object.create(RealWebSocket.prototype);
  RealWebSocket.apply(websocket, arguments);

[Wladimir Palant, 2016/08/15 12:45:36]

This will also allow dropping protocols parameter from the function signature -
then WebSocket.length will match the real thing.

[Wladimir Palant, 2016/08/15 13:01:24]

Never mind, calling RealWebSocket.apply() won't work no matter what you pass in
- detecting function call vs. new there doesn't work by checking this pointer.
So avoiding assumptions about parameters here requires spread operator which
sadly isn't supported before Chrome 46 or Safari 7.1, not worth it.

[Sebastian Noack, 2016/08/15 13:06:10]

See patchset #2 (and the related discussin) for a compatible way to pass
variable arguments.

 
       checkRequest(websocket.url, function(blocked)
       {
         if (blocked)
           closeWebSocket(websocket);
       });
 
       return websocket;
     }.bind();
 
@@ skipping 194 matching lines @@
   }, true);
 
   return updateStylesheet;
 }
 
 if (document instanceof HTMLDocument)
 {
   checkSitekey();
   window.updateStylesheet = init(document);
 }