//    (hypothetical) unsafe read by our caller. Note: adding 'volatile' does not fix this issue,
  //    it would just add an edge such that if done() observed non-null, then it would also
  //    definitely observe all earlier writes, but we still have no guarantee that done() would see
  //    the initial write (just stronger guarantees if it does).
  //
  // See: http://cs.oswego.edu/pipermail/concurrency-interest/2015-January/013800.html

    return new HashSet<>(Maps.capacity(expectedSize));
  }

  /**
   * Creates a thread-safe set backed by a hash map. The set is backed by a {@link
   * ConcurrentHashMap} instance, and thus carries the same concurrency guarantees.
   *
   * <p>Unlike {@code HashSet}, this class does NOT allow {@code null} to be used as an element. The
   * set is serializable.
   *
   * @return a new, empty thread-safe {@code Set}

    enableTlsWithTunnel()
    server.protocols = Arrays.asList(Protocol.HTTP_2, Protocol.HTTP_1_1)
    timeToFirstByte()
  }

  /**
   * Test to confirm that events are reported at the time they occur and no earlier and no later.
   * This inserts a bunch of synthetic 250 ms delays into both client and server and confirms that
   * the same delays make it back into the events.
   *

    methods track the system's local time when network calls are made. These
    replace the `OkHttp-Sent-Millis` and `OkHttp-Received-Millis` headers that were
    present in earlier versions of OkHttp.
 *  New: Accept user-provided trust managers in `OkHttpClient.Builder`. This
    allows OkHttp to satisfy its TLS requirements directly. Otherwise OkHttp