RFR: 8299031: JFR: Clean up jdk.management.jfr

[Erik Gahlin]

Could I have a review of change that remove an unused method and add pattern matching for instanceof

Thanks
Erik

-------------

Commit messages:
 - Initial

Changes: https://git.openjdk.org/jdk/pull/11724/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=11724&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299031
  Stats: 23 lines in 4 files changed: 0 ins; 12 del; 11 mod
  Patch: https://git.openjdk.org/jdk/pull/11724.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11724/head:pull/11724

PR: https://git.openjdk.org/jdk/pull/11724