hg: shenandoah/jdk8u/hotspot: [backport] Full GC should not trash empty regions

[ashipile at redhat.com]

Changeset: 50ff7aaa7472
Author:    shade
Date:      2018-03-20 16:25 +0100
URL:       http://hg.openjdk.java.net/shenandoah/jdk8u/hotspot/rev/50ff7aaa7472

[backport] Full GC should not trash empty regions

! src/share/vm/gc_implementation/shenandoah/shenandoahHeapRegion.cpp
! src/share/vm/gc_implementation/shenandoah/shenandoahHeapRegion.hpp
! src/share/vm/gc_implementation/shenandoah/shenandoahMarkCompact.cpp