RFR: 8144992: Remove OopIterateClosure::idempotent

[Kim Barrett]

> On Jun 25, 2018, at 9:58 AM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> Hi all,
> 
> Please review this patch to remove the OopIterateClosure::idempotent() function.
> 
> http://cr.openjdk.java.net/~stefank/8144992/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8144992
> 
> There's no closure that overrides idempotent() anymore, so this patch removes the function an all usages.
> 
> Thanks,
> StefanK

Looks good.