RFR: Upstream merge to jdk-12+12

[Aleksey Shipilev]

On 09/20/2018 01:29 PM, Roman Kennke wrote:
> This merges changes from jdk/jdk into sh/jdk, up to tag jdk-12+12.
> 
> http://cr.openjdk.java.net/~rkennke/upstream-merge-2018-08-19/outgoing.txt

Looks good.

> Notable changes:
> 8210713: Let CollectedHeap::ensure_parsability() take care of TLAB
> statistics gathering

It would probably clash with my shenandoahHeap.hpp reshuffling, but that's okay.

-Aleksey