RFR: 8298588: WebSockets: HandshakeUrlEncodingTest unnecessarily depends on a response body

Tue Dec 13 07:59:58 UTC 2022

According to [rfc6455](https://www.rfc-editor.org/rfc/rfc6455.html#section-5.5.1), the close frame MAY contain a body, i.e. it is considered [optional](https://www.rfc-editor.org/rfc/rfc2119#section-5). It seems that the contemporary JDK HEAD (tip) does populate the body and thus enables `HandshakeUrlEncodingTest.java` to parse its contents. On the contrary, JDK 11 does not populate the body in the same case. I would like to backport JDK-8245245 all the way to JDK 11, so I would like to change the behavior of this test so as it works across JDK versions.

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Commit messages:
 - WebSockets: Makes HandshakeUrlEncodingTest JDK version agnostic

Changes: https://git.openjdk.org/jdk/pull/11486/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11486&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8298588
  Stats: 12 lines in 1 file changed: 4 ins; 6 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/11486.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11486/head:pull/11486

PR: https://git.openjdk.org/jdk/pull/11486