RFR: Remove ShenandoahWriteBarrierCsetTestInIR flag

[Aleksey Shipilev]

On 11/19/18 10:42 AM, Roman Kennke wrote:
> This is actually a prerequisite to removing the wb-stub for C2, because
> if we don't call via the stub, we can't do the cset there. We've no use
> for this flag anyway, doing cset test in ideal is what we do since a
> long time. Let's remove it.
> 
> http://cr.openjdk.java.net/~rkennke/remove-cset-in-ideal-flag/webrev.00/

Looks good. Please rebase the other change ("avoid stub") after this?

-Aleksey