RFR: Refactor conc-mark-in-progress/satb-active flags to use gc-phase-in-progress

[Aleksey Shipilev]

On 09/25/2017 06:59 PM, Roman Kennke wrote:
> http://cr.openjdk.java.net/~rkennke/satb-concmark-flag/webrev.02/

So I am not happy with refactoring G1 codepaths: this will pose problems with merging from upstream,
problems with backports, problems with testing, etc. Copy-paste Shenandoah paths out (that would
probably disentangle Shenandoah going via g1_* stubs too?), and then we wait for GC interface to
arrive to remove that copy-paste.

Thanks,
-Aleksey