RFR (M): 8208498: Put archive regions into a first-class HeapRegionSet

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that adds a seperate HeapRegionSet
for archive regions.

This will simplify getting information about them in the future.

CR:
https://bugs.openjdk.java.net/browse/JDK-8208498
Webrev:
http://cr.openjdk.java.net/~tschatzl/8208498/webrev/
Testing:
hs-tier1-4, jdk-tier1-3

Thanks,
  Thomas