RFR 8204947: Port ShenandoahTaskTerminator to mainline and make it default

[Kim Barrett]

> On Nov 28, 2018, at 3:45 PM, Roman Kennke <rkennke at redhat.com> wrote:
> 
> I believe if you add a flag, you need to file a CSR.

Experimental and diagnositc options don't need a CSR.  From the CSR FAQ: 
https://wiki.openjdk.java.net/display/csr/CSR+FAQs

"Interfaces that are experimental or for diagnostic purposes do not
need to go through CSR process, but the CSR process may be employed if
feedback from the CSR reviewers is desired."

That's a relatively recent change (this calendar year).

I also think what's being proposed here is more of a diagnostic than
experimental flag.  I think an experimental flag ought to be opt-in,
e.g. off by default but one can choose to take the risk.  A diagnostic
flag can be used to opt-out of the "normal" behavior, in this case to
revert back to the old behavior.  Of course, we violate that a lot...