[jdk11u-dev] RFR: 8306955: Open source several JComboBox jtreg tests

[Andrew Lu]

I backport this for parity with 11.0.21-oracle.

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

Commit messages:
 - Backport 1f689241cfcb4083cba283a2010b532948865283

Changes: https://git.openjdk.org/jdk11u-dev/pull/2072/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2072&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306955
  Stats: 392 lines in 5 files changed: 392 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2072.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2072/head:pull/2072

PR: https://git.openjdk.org/jdk11u-dev/pull/2072