[jdk11u-dev] RFR: 8253543: sanity/client/SwingSet/src/ButtonDemoScreenshotTest.java failed with "AssertionError: All pixels are not black"

[Andrew Lu]

I backport this for parity with 11.0.23-oracle.

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Commit messages:
 - Backport ffc97ba585b3750a0fe0d29d39a1201d91954d0f

Changes: https://git.openjdk.org/jdk11u-dev/pull/2403/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2403&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8253543
  Stats: 139 lines in 4 files changed: 95 ins; 18 del; 26 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2403.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2403/head:pull/2403

PR: https://git.openjdk.org/jdk11u-dev/pull/2403