rws := http2responseWriterStatePool.Get().(*http2responseWriterState)
	bwSave := rws.bw
	*rws = http2responseWriterState{} // zero all the fields
	rws.conn = sc
	rws.bw = bwSave
	rws.bw.Reset(http2chunkWriter{rws})
	rws.stream = st
	rws.req = req
	return &http2responseWriter{rws: rws}
}

type http2unstartedHandler struct {
	streamID uint32