func NewClient(uu *url.URL, tr http.RoundTripper, newAuthToken func(aud string) string) *Client {
	connected := int32(online)
	urlStr := uu.String()
	u, err := url.Parse(urlStr)
	if err != nil {
		// Mark offline, with no reconnection attempts.
		connected = int32(offline)
		err = &url.Error{URL: urlStr, Err: err}
	}
	// The host's colon:port should be normalized. See Issue 14836.
	u.Host = removeEmptyPort(u.Host)