RFR: 8254090: Collectors.toUnmodifiableList exposes shared secret

[Stuart Marks]

Add check for ArrayList.class before passing it to the shared secret.

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Commit messages:
 - update copyright on test
 - 8254090: Collectors.toUnmodifiableList exposes shared secret

Changes: https://git.openjdk.java.net/jdk/pull/569/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=569&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8254090
  Stats: 60 lines in 2 files changed: 58 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/569.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/569/head:pull/569

PR: https://git.openjdk.java.net/jdk/pull/569