RFR: Keep root bits until the end of partial

[Zhengyu Gu]

Okay.

-Zhengyu

On 06/14/2017 09:31 AM, Aleksey Shipilev wrote:
> We need to keep region->is_root bit until partial is over, because otherwise
> hs_err from the mid-partial crash looks misleading: it could say that some
> region is not root, while it actually is!
>
> See:
>   http://cr.openjdk.java.net/~shade/shenandoah/partial-keeproots/webrev.01/
>
> Thanks,
> -Aleksey
>