[foreign] RFR 8219119: Need API to create a null Callback

[Maurizio Cimadamore]

Looks good - but I think it can be simplified further - there's no need 
to accept a carrier type in Callback::ofNull.

You can just create a CallbackImpl which throws NPE whenever you try to 
call 'asFunction'.

Maurizio

On 15/02/2019 17:00, Sundararajan Athijegannathan wrote:
> Please review.
>
> Bug: https://bugs.openjdk.java.net/browse/JDK-8219119
> Webrev: https://cr.openjdk.java.net/~sundar/8219119/webrev.00/
>
> Thanks,
> -Sundar