8201490: Improve concurrent mark keep alive closure performance
Summary: Avoid doing marking work unless absolutely required.
Reviewed-by: sjohanss, kbarrett
^build/
^dist/
^.idea/
nbproject/private/
^webrev
^.src-rev$
^.jib/
\.DS_Store
\.metadata/
\.recommenders/
test/nashorn/script/external
test/nashorn/lib
NashornProfile.txt
.*/JTreport/.*
.*/JTwork/.*