RFR: 8342734: GenShen: Test failure gc/shenandoah/TestReferenceRefersToShenandoah.java#generational [v2]

[William Kemper]

> Recent change introduced a regression: https://bugs.openjdk.org/browse/JDK-8342560 that caused old regions to not belong to global collections.

William Kemper has updated the pull request incrementally with one additional commit since the last revision:

  Comment improvements

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Changes:
  - all: https://git.openjdk.org/shenandoah/pull/527/files
  - new: https://git.openjdk.org/shenandoah/pull/527/files/238be83d..65af911f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=shenandoah&pr=527&range=01
 - incr: https://webrevs.openjdk.org/?repo=shenandoah&pr=527&range=00-01

  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/shenandoah/pull/527.diff
  Fetch: git fetch https://git.openjdk.org/shenandoah.git pull/527/head:pull/527

PR: https://git.openjdk.org/shenandoah/pull/527