function WebSocketRequest(httpRequest) {
  // We'll assume control of the socket for this request.
  HttpRequest.apply(this, [httpRequest.headers, httpRequest.pSocket_]);
  httpRequest.pSocket_ = null;
}
Constructs a WebSocket request object from an Http request. This invalidates
the Http request's socket and offers accept and reject methods for accepting
and rejecting the WebSocket upgrade request.
@param {HttpRequest} httpRequest The HTTP request to upgrade.