RFR: 8315600: Open source few more headless Swing misc tests [v3]

[Prasanta Sadhukhan]

> Few more closed swing headless tests are opensourced

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  Minor optimization

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Changes:
  - all: https://git.openjdk.org/jdk/pull/15582/files
  - new: https://git.openjdk.org/jdk/pull/15582/files/0c7c44b9..fccec782

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=15582&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=15582&range=01-02

  Stats: 27 lines in 3 files changed: 8 ins; 7 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/15582.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15582/head:pull/15582

PR: https://git.openjdk.org/jdk/pull/15582