<Swing Dev> RFR: 8198395: Test javax/swing/plaf/metal/MetalLookAndFeel/Test8039750.java fails in mach5

[Prasanta Sadhukhan]

Please review a test fix for an issue seen to be failing in mach5.
Test is stabilised by making the test run under EDT.
Mach5 job was run for several iteration on all 3 platforms. Link in JBS

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Commit messages:
 - Fixed jcheck issue
 - 8198395: Test javax/swing/plaf/metal/MetalLookAndFeel/Test8039750.java fails in mach5

Changes: https://git.openjdk.java.net/jdk/pull/715/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=715&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8198395
  Stats: 30 lines in 2 files changed: 3 ins; 1 del; 26 mod
  Patch: https://git.openjdk.java.net/jdk/pull/715.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/715/head:pull/715

PR: https://git.openjdk.java.net/jdk/pull/715