RFR: 8151696: Print all regions on trace level to get same behavior as old PrintHeapAtGCExtended

[Stefan Johansson]

Hi,

Please review this change for RFE:
https://bugs.openjdk.java.net/browse/JDK-8151696

Webrev:
http://cr.openjdk.java.net/~sjohanss/8151696/hotspot.00/

Summary:
After UL there was no way to turn on logging to get the same output as 
PrintHeapAtGCExtended had in the past. This change adds functionality 
back by printing regions on trace level for the tag-set (gc, heap, 
region). I've run the gc jtreg tests as sanity checking and the tests pass.

Thanks,
Stefan