/** Expose this recorder as a frame callback and shim in "ping" events.  */
  fun asFrameCallback() =
    object : WebSocketReader.FrameCallback {
      override fun onReadMessage(text: String) {
        events.add(Message(string = text))
      }

      override fun onReadMessage(bytes: ByteString) {
        events.add(Message(bytes = bytes))
      }

      override fun onReadPing(payload: ByteString) {