[jdk11u-dev] RFR: 8282789: Create a regression test for the JTree usecase of JDK-4618767

[Goetz Lindenmaier]

I backport this for parity with 11.0.17-oracle.

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Commit messages:
 - Backport 83a1c90433343107eaa2a7fa41b9b07f86b6ce19

Changes: https://git.openjdk.org/jdk11u-dev/pull/1286/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1286&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8282789
  Stats: 226 lines in 1 file changed: 226 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1286.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1286/head:pull/1286

PR: https://git.openjdk.org/jdk11u-dev/pull/1286