<i18n dev> RFR: 8311030: ResourceBundle.handleKeySet() is racy

[Sergey Tsypanov]

Double-checked locking should rely on local variable to avoid racy reads from volatile field.

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Commit messages:
 - 8311030: ResourceBundle.handleKeySet() is racy

Changes: https://git.openjdk.org/jdk/pull/14692/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14692&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311030
  Stats: 4 lines in 1 file changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/14692.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14692/head:pull/14692

PR: https://git.openjdk.org/jdk/pull/14692