title: Sockjs fallback with Spring Security CSRF enable
body: <p><br/>
  My project use Spring Security + Spring MVC and deals with websocket (over stomp+sockjs). <br/>
  When I test the sockjs fallback the XHR request return 403.
  If I turn off csrf on the security context it's OK.<br/>
  If I override the sockjs AbstractXHRObject constructor like this : it's ok :</p>
  
  <pre><code>function AbstractXHRObject(method, url, payload, opts) {
    debug(method, url);
    var self = this;
    EventEmitter.call(this);
  
    // HACK : add csrf headers
    opts["headers"][csrfHeader] = csrfToken;
  
    setTimeout(function () {
      self._start(method, url, payload, opts);
    }, 0);
  }
  </code></pre>
  
  <p><em>Off course I have to check if opts is not null...</em></p>
  
  <p>My question is : <strong>What is the way to add headers on the XHR fallback object of SockJS</strong> ?</p>
  
  <p>Thanks</p>