RFR (round 1), JDK-8214259: Implementation: JEP 189: Shenandoah: A Low-Pause Garbage Collector

[Zhengyu Gu]

Hi Kim,

> 
>>      - taskqueue.hpp has some small adjustments to enable subclassing
> 
> Why this change instead of JDK-8204947?  As the description from that RFE says:
> "The ShenandoahTaskTerminator from the Shenandoah project is a much better implementation of a task terminator.”
> 
We were busy on preparing Shenandoah for upstreaming, this did take a 
back seat.

I am going to start to work on moving ShenandoahTaskTerminator to share 
tomorrow, but it should not hold up the review.

Thanks,

-Zhengyu