TODO:
According to http://www.w3.org/TR/XMLHttpRequest/, methods and fields

  void               open(in DOMString method, in DOMString url, in boolean async, in DOMString user);
  void               open(in DOMString method, in DOMString url, in boolean async, in DOMString user, in DOMString password);
  void               send(in Document data);
  void               abort();
  DOMString          getAllResponseHeaders();
  readonly attribute unsigned short  status;
  readonly attribute DOMString       statusText;

are missing.