RFR: 8283558: Parallel: Pass PSIsAliveClosure to ReferenceProcessor constructor

[Albert Mingkun Yang]

Simple change around non-strong ref discovery in young-gc ref-processing.

Test: tier1-6

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Commit messages:
 - ps-is-alive-closure

Changes: https://git.openjdk.java.net/jdk/pull/7918/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7918&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283558
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7918.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7918/head:pull/7918

PR: https://git.openjdk.java.net/jdk/pull/7918