Changes ForkJoinPool.close spec and code to trap close as a no-op if called on common pool
------------- Commit messages: - Override close as explicit no-op for common pool Changes: https://git.openjdk.java.net/jdk/pull/8577/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8577&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8286294 Stats: 75 lines in 2 files changed: 75 ins; 0 del; 0 mod Patch: https://git.openjdk.java.net/jdk/pull/8577.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/8577/head:pull/8577 PR: https://git.openjdk.java.net/jdk/pull/8577
