RFR: 8196325: GarbageCollectionNotificationInfo has same information for before and after

[sangheon.kim]

Hi all,

Could I have some reviews for this patch?

GarbageCollectionNotificationInfo is printing same used size at Eden 
space before and after GC. But the problem is that memory pool names and 
actual GC information(including memory usage) are not matching. So the 
printed memory usage at Eden is actually metaspace memory usage in my case.

Proposed patch is adding a new API to get all memory pool names without 
changing memory order.
Enhanced existing JTREG test, to check used size change at Eden space.

CR: https://bugs.openjdk.java.net/browse/JDK-8196325
webrev: http://cr.openjdk.java.net/~sangheki/8196325/webrev.0/
Testing: jdk-tier1,jdk-tier2,jdk-tier3,hs-tier1,hs-tier2,builds-tier1, 
jdk_management, jdk_jmx

Thanks,
Sangheon