RFR: 8281289: Improve with List.copyOf

[Xue-Lei Andrew Fan]

Please review this trivial code clean up, for a little bit better performance.

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Commit messages:
 - 8281289: Improve with List.copyOf

Changes: https://git.openjdk.java.net/jdk/pull/7356/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7356&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8281289
  Stats: 5 lines in 1 file changed: 0 ins; 3 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7356.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7356/head:pull/7356

PR: https://git.openjdk.java.net/jdk/pull/7356