type http2Framer struct {
	r         io.Reader
	lastFrame http2Frame
	errDetail error

	// countError is a non-nil func that's called on a frame parse
	// error with some unique error path token. It's initialized
	// from Transport.CountError or Server.CountError.
	countError func(errToken string)

	// lastHeaderStream is non-zero if the last frame was an
	// unfinished HEADERS/CONTINUATION.