RFR (XS): 8183397: Ensure consistent closure filtering during evacuation

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that fixes an observation that has
been made recently by Erik, i.e. that the "else" part of several
evacuation closures inconsistently filters out non-cross-region
references before checking whether the referenced object is a humongous
or ext region.

This causes somewhat hard to diagnose performance issues, and earlier
filtering does not hurt if done anyway.

(Note that the current way of checking in all but the UpdateRS closure
using HeapRegion::is_in_same_region() seems optimal. The only reason
why the other way in the UpdateRS closure is better because the code
needs the "to" HeapRegion pointer anyway)

CR:
https://bugs.openjdk.java.net/browse/JDK-8183397
Webrev:
http://cr.openjdk.java.net/~tschatzl/8183397/webrev/
Testing:
jprt, performance regression analysis

Thanks,
  Thomas