[jdk11u-dev] RFR: 8285698: Create a test to check the focus stealing of JPopupMenu from JComboBox

[Goetz Lindenmaier]

I backport this for parity with 11.0.17-oracle.

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Commit messages:
 - Backport 7612bba0f1ae63b2c762eb103544dc43d4e8304f

Changes: https://git.openjdk.org/jdk11u-dev/pull/1367/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1367&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8285698
  Stats: 179 lines in 1 file changed: 179 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1367.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1367/head:pull/1367

PR: https://git.openjdk.org/jdk11u-dev/pull/1367