docs: function initialize(url) {
      this.socket = Requests[Requests.method](this);
  
      //
      // Open the socket BEFORE adding any properties to the instance as this might
      // trigger a thrown `InvalidStateError: An attempt was made to use an object
      // that is not, or is no longer, usable` error in FireFox:
      //
      // @see https://bugzilla.mozilla.org/show_bug.cgi?id=707484
      //
      this.socket.open(this.method.toUpperCase(), url, true);
  
      //
      // Register this as an active HTTP request.
      //
      Requests.active[this.id] = this;
    }