git: openjdk/mobile: 8235905: ZGC: Rework how ZRootsIterator visits threads

[duke]

Changeset: bd6ab22a
Author:    Per Lidén <pliden at openjdk.org>
Date:      2019-12-17 11:37:55 +0000
URL:       https://git.openjdk.java.net/mobile/commit/bd6ab22a

8235905: ZGC: Rework how ZRootsIterator visits threads

Reviewed-by: stefank

! src/hotspot/share/gc/z/zRootsIterator.cpp
! src/hotspot/share/gc/z/zRootsIterator.hpp
! src/hotspot/share/runtime/threadSMR.hpp