[jdk11u-dev] RFR: 7148092: [macosx] When Alt+down arrow key is pressed, the combobox popup does not appear.

[Andrew Lu]

I backport this for parity with 11.0.23-oracle.

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Commit messages:
 - Backport c42ef70a453690ecdccc570161fdfda58318ecc6
 - Backport c42ef70a453690ecdccc570161fdfda58318ecc6

Changes: https://git.openjdk.org/jdk11u-dev/pull/2347/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2347&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-7148092
  Stats: 128 lines in 3 files changed: 128 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2347.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2347/head:pull/2347

PR: https://git.openjdk.org/jdk11u-dev/pull/2347