RFR: 8015444: closed/java/awt/Focus/KeyStrokeTest/KeyStrokeTest.html sometimes fails

[Prasanta Sadhukhan]

Although the test doesn't fail in recent run, test is updated to use CountDownLatch with proper delay and frame being made to render to screen centre. 
Several iterations of the test is ok, test job in JBS

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Commit messages:
 - 8015444: closed/java/awt/Focus/KeyStrokeTest/KeyStrokeTest.html sometimes fails

Changes: https://git.openjdk.org/jdk/pull/27182/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27182&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8015444
  Stats: 70 lines in 1 file changed: 32 ins; 29 del; 9 mod
  Patch: https://git.openjdk.org/jdk/pull/27182.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27182/head:pull/27182

PR: https://git.openjdk.org/jdk/pull/27182