hg: shenandoah/jdk: Cherry-pick 8204947: Port ShenandoahTaskTerminator to mainline and make it default

[zgu at redhat.com]

Changeset: 2d682f8bfcfc
Author:    zgu
Date:      2018-12-07 16:04 -0500
URL:       http://hg.openjdk.java.net/shenandoah/jdk/rev/2d682f8bfcfc

Cherry-pick 8204947: Port ShenandoahTaskTerminator to mainline and make it default
Reviewed-by: tschatzl, rkennke

! src/hotspot/share/gc/cms/concurrentMarkSweepGeneration.cpp
! src/hotspot/share/gc/cms/parNewGeneration.cpp
! src/hotspot/share/gc/cms/parNewGeneration.hpp
! src/hotspot/share/gc/g1/g1CollectedHeap.cpp
! src/hotspot/share/gc/g1/g1ConcurrentMark.cpp
! src/hotspot/share/gc/g1/g1ConcurrentMark.hpp
! src/hotspot/share/gc/g1/g1FullGCMarkTask.cpp
! src/hotspot/share/gc/g1/g1FullGCMarkTask.hpp
! src/hotspot/share/gc/g1/g1FullGCReferenceProcessorExecutor.hpp
! src/hotspot/share/gc/parallel/pcTasks.cpp
! src/hotspot/share/gc/parallel/psParallelCompact.cpp
! src/hotspot/share/gc/parallel/psScavenge.cpp
! src/hotspot/share/gc/shared/gc_globals.hpp
+ src/hotspot/share/gc/shared/owstTaskTerminator.cpp
+ src/hotspot/share/gc/shared/owstTaskTerminator.hpp
! src/hotspot/share/gc/shared/taskqueue.cpp
! src/hotspot/share/gc/shared/taskqueue.hpp