RFR: 8304164: jdk/classfile/CorpusTest.java still fails after JDK-8303910

[Adam Sotona]

Massive parallel execution of parametrised CorpusTest junit tests revealed race condition in `ClassHierarchyImpl.CachedClassHierarchyResolver::getClassInfo`.

The race condition may skip calculation of the ClassHierarchyInfo. In this specific case it caused SegmentScope not being identified as an interface and verify error on assignability between declared method return type and actual returned type has been emitted by the test.

Proposed patch fixes the race condition in `ClassHierarchyImpl.CachedClassHierarchyResolver::getClassInfo`.

Please review.

Thank you,
Adam

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Commit messages:
 - 8304164: jdk/classfile/CorpusTest.java still fails after JDK-8303910

Changes: https://git.openjdk.org/jdk/pull/13037/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13037&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304164
  Stats: 9 lines in 1 file changed: 6 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/13037.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/13037/head:pull/13037

PR: https://git.openjdk.org/jdk/pull/13037