RFR: 8283513: Parallel: Skip the card marking in PSRootsClosure

[Albert Mingkun Yang]

This PR consists of two commits:

1. Skip card marking in `PSRootsClosure`
2. Make in-heap `oop*` a precondition of `copy_and_push_safe_barrier`

Test: tier1-3

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

Commit messages:
 - off-heap check
 - ps-root-closure

Changes: https://git.openjdk.java.net/jdk/pull/7903/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7903&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283513
  Stats: 21 lines in 3 files changed: 8 ins; 7 del; 6 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7903.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7903/head:pull/7903

PR: https://git.openjdk.java.net/jdk/pull/7903