RFR: Backport 8195115: G1 Old Gen MemoryPool CollectionUsage.used values don't reflect mixed GC results

[Hohensee, Paul]

Please review a backport to jdk8u.

Bug: https://bugs.openjdk.java.net/browse/JDK-8195115
Webrev: http://cr.openjdk.java.net/~phh/8195115/webrev.05/
JDK11 patch: http://hg.openjdk.java.net/jdk/jdk/rev/5d3c5af82654

The backport is slightly different from the JDK11 patch due to G1 refactoring, hence my request for new review. I’ll ask for jdk8u approval once the backport is reviewed.

I backported two jtreg tests from JDK11, which pass. Also, all the hotspot gc jtreg tests pass as well as they do for jdk8u-dev.

There was a CSR involved, https://bugs.openjdk.java.net/browse/JDK-8196719. Does that have to be re-approved for jdk8u as well, and if so, what’s the process?

Thanks,

Paul