RFR (7xS): 8071280: Specialize HeapRegion::oops_on_card_seq_iterate_careful() for use during concurrent refinement and updating the rset

[Kim Barrett]

> On May 15, 2017, at 7:19 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> 
> Webrevs:
> http://cr.openjdk.java.net/~tschatzl/8071280/webrev.1_to_2/ (diff)
> http://cr.openjdk.java.net/~tschatzl/8071280/webrev.2/ (full)
> 
> Testing:
> jprt, gc/common tier 1-5 tests with and without
> ClassUnloadingWithConcurrentMark

Thanks for verifying the ClassUnloadingWithConcurrentMark case.

Looks good.