anchor.diff:     * [url].
      *
      * The `Host` header for the request will be set to the value
  -   * [Uri.host]:[Uri.port] from [url]. This can be overridden through the
  -   * [HttpClientRequest] interface before the request is sent.  NOTE
  -   * if [Uri.host] is an IP address this will still be set in the `Host`
  -   * header.
  +   * [Uri.host]:[Uri.port] from [url] (if [url.host] is an IP address, it will
  +   * still be used in the `Host` header). This can be overridden through the
  +   * [HttpClientRequest] interface before the request is sent.
      *
      * For additional information on the sequence of events during an
      * HTTP transaction, and the objects returned by the futures, see
  
positive.code:   /**
     * Gets and sets the content length of the response. If the size of
     * the response is not known in advance set the content length to
     * -1 - which is also the default if not set.
     */
    int contentLength;
  
  
negative.code:    * the response body is not known in advance.
     *
     * If the content length needs to be set, it must be set before the
     * body is written to. Setting the content length after writing to the body
     * will throw a `StateError`.
     */
    int get contentLength;
  
    /**
     * Gets the persistent connection state returned by the server.
     *
     * If the persistent connection state needs to be set, it must be
     * set before the body is written to. Setting the persistent connection state
     * after writing to the body will throw a `StateError`.
     */
    bool get persistentConnection;
  