RFR: 8292969: Bad Thread Utilization in ForkJoinPool

[Doug Lea]

8292969: This small change in signal propagation rules improves utilization when entry queues are resized,

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Commit messages:
 - Merge remote-tracking branch 'refs/remotes/origin/JDK-8292969' into JDK-8292969
 - Merge branch 'openjdk:master' into JDK-8292969
 - Update @preturn javadoc to reflect use of prevSrc
 - Improve signal propagation after queue resizing

Changes: https://git.openjdk.org/jdk/pull/10198/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=10198&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8292969
  Stats: 6 lines in 1 file changed: 1 ins; 0 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/10198.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10198/head:pull/10198

PR: https://git.openjdk.org/jdk/pull/10198