*        * body ([requestBodyStart], [requestBodyEnd])
 *      * response ([responseFailed])
 *        * headers ([responseHeadersStart], [responseHeadersEnd])
 *        * body ([responseBodyStart], [responseBodyEnd])
 *
 * This nesting is typical but not strict. For example, when calls use "Expect: continue" the
 * request body start and end events occur within the response header events. Similarly,