RFR: 8225131: Test DragSourceMotionListenerTest.java fails on Windows

[Tejesh R]

Test is failing frequently on mach5 machines. I have fixed it with stabilizations and moved the frame to center of the screen. After the fix several runs were made on mach5 and no failures were seen.

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Commit messages:
 - Stabilization fix

Changes: https://git.openjdk.org/jdk/pull/27283/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=27283&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8225131
  Stats: 22 lines in 2 files changed: 15 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/27283.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27283/head:pull/27283

PR: https://git.openjdk.org/jdk/pull/27283