hg: jdk/sandbox: 8237632: Shenandoah: accept NULL fwdptr to cooperate with JVMTI and JFR

[chris.hegarty at oracle.com]

Changeset: b5745158500a
Author:    zgu
Date:      2020-02-26 15:32 -0500
URL:       https://hg.openjdk.java.net/jdk/sandbox/rev/b5745158500a

8237632: Shenandoah: accept NULL fwdptr to cooperate with JVMTI and JFR
Reviewed-by: shade, rkennke

! src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp
! src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.hpp
! src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.inline.hpp
! src/hotspot/share/gc/shenandoah/shenandoahForwarding.hpp
! src/hotspot/share/gc/shenandoah/shenandoahForwarding.inline.hpp
! src/hotspot/share/gc/shenandoah/shenandoahHeap.cpp
! src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.cpp
! src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.hpp