rest/jsonp.go
func (w *jsonpResponseWriter) Flush() {
	if !w.wroteHeader {
		w.WriteHeader(http.StatusOK)
	}
	flusher := w.ResponseWriter.(http.Flusher)
	flusher.Flush()
}
func (w *jsonpResponseWriter) Flush() {
	if !w.wroteHeader {
		w.WriteHeader(http.StatusOK)
	}
	flusher := w.ResponseWriter.(http.Flusher)
	flusher.Flush()
}
// Make sure the local WriteHeader is called, and call the parent Flush.
// Provided in order to implement the http.Flusher interface.