[jdk21u-dev] RFR: 8328697: SubMenuShowTest and SwallowKeyEvents tests stabilization

[Andrew Lu]

I backport this for parity with 21.0.5-oracle.

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

Commit messages:
 - Backport 638708cad8228f62caf633015973403164675560

Changes: https://git.openjdk.org/jdk21u-dev/pull/785/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=785&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8328697
  Stats: 58 lines in 2 files changed: 29 ins; 27 del; 2 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/785.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/785/head:pull/785

PR: https://git.openjdk.org/jdk21u-dev/pull/785