RFR: 8353592: Open source several scrollbar tests

[Alexander Zvegintsev]

Few scroll bar tests are open sourced. Testing looks good.

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Commit messages:
 - initial

Changes: https://git.openjdk.org/jdk/pull/24590/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24590&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353592
  Stats: 382 lines in 3 files changed: 382 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24590.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24590/head:pull/24590

PR: https://git.openjdk.org/jdk/pull/24590