<Swing Dev> RFR: 8199079: Test javax/swing/UIDefaults/6302464/bug6302464.java is unstable

[Prasanta Sadhukhan]

This test was marked as unstable in CI run in samevm mode but later on was found passing in now-default othervm mode but was problemlisted only on macos by JDK-8254976.
It is found that this test started failing in macos due to JDK-8220150:  [macos] macos10.14 Mojave returns anti-aliased glyphs instead of aliased B&W glyphs
which turns Antialias hint even if it is set to off from macosx10.14 onwards.
So, this test started failing when it tries to test Antialias OFF hint.

Proposed fix is to check for macosx 10.14 and greater version and bail out from this subtest.

@prrace Can you please take a look?

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Commit messages:
 - 8199079: Test javax/swing/UIDefaults/6302464/bug6302464.java is unstable

Changes: https://git.openjdk.java.net/jdk/pull/3537/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3537&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8199079
  Stats: 26 lines in 2 files changed: 18 ins; 1 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3537.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3537/head:pull/3537

PR: https://git.openjdk.java.net/jdk/pull/3537