RFR: 8194406: Use Atomic::replace_if_null

[coleen.phillimore at oracle.com]

Looks good.
Coleen

On 1/2/18 11:02 PM, Kim Barrett wrote:
> Please review this change to use Atomic::replace_if_null where
> applicable.
>
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8194406
>
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8194406/open.00/
>
> Testing:
> Mach5 hs-tier1,2,3
>