RFR: Relax assert in SBS::is_safe()

[Aleksey Shipilev]

On 01/24/2018 03:12 PM, Roman Kennke wrote:
> With traversal I am hitting the assert in SBS::is_safe() (through weakref discovery) because GC got
> cancelled and the obj is not in to-space. It is not a problem with conc-mark because there we don't
> evac during marking.
> 
> The fix is to fall-through the in_cset() check when GC got cancelled, and check if there is an
> actual copy.
> 
> http://cr.openjdk.java.net/~rkennke/fixissafe/webrev.00/

Makes sense.

Thanks,
-Aleksey