// also treated as unknown.
	ContentLength int64

	// TransferEncoding lists the transfer encodings from outermost to
	// innermost. An empty list denotes the "identity" encoding.
	// TransferEncoding can usually be ignored; chunked encoding is
	// automatically added and removed as necessary when sending and
	// receiving requests.
	TransferEncoding []string

	// Close indicates whether to close the connection after

		if r.Method == "GET" && r.FormValue("mode") == "hangup" {
			c, _, _ := w.(http.Hijacker).Hijack()
			c.Close()
			return
		}
		if len(r.TransferEncoding) > 0 {
			t.Errorf("backend got unexpected TransferEncoding: %v", r.TransferEncoding)
		}
		if r.Header.Get("X-Forwarded-For") == "" {
			t.Errorf("didn't get X-Forwarded-For header")
		}
		if c := r.Header.Get("Connection"); c != "" {