Create a automated regression test for JComboBox titled border issues([JDK-8300269](https://bugs.openjdk.org/browse/JDK-8300269)).
This test passes in JDK-20-ea+16 and fails in JDK-20-ea+16 and above. ------------- Commit messages: - 8300409: Create an automated regression test for JComboBox titled border issues(JDK-8300269) Changes: https://git.openjdk.org/jdk/pull/12061/files Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=12061&range=00 Issue: https://bugs.openjdk.org/browse/JDK-8300409 Stats: 176 lines in 1 file changed: 176 ins; 0 del; 0 mod Patch: https://git.openjdk.org/jdk/pull/12061.diff Fetch: git fetch https://git.openjdk.org/jdk pull/12061/head:pull/12061 PR: https://git.openjdk.org/jdk/pull/12061
