RFR: JDK-8319662 ForkJoinPool trims worker threads too slowly [v5]

[Doug Lea]

> This update cascades timeouts to trim subsequent workers after the first  keepAlive inactive period.

Doug Lea has updated the pull request incrementally with one additional commit since the last revision:

  Revert 2 lines in method scan

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/16725/files
  - new: https://git.openjdk.org/jdk/pull/16725/files/149304e7..e111166f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16725&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16725&range=03-04

  Stats: 5 lines in 1 file changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/16725.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16725/head:pull/16725

PR: https://git.openjdk.org/jdk/pull/16725