RFR (M) 8235573: Move JFR ObjectSample oop into OopStorage

[Kim Barrett]

> On Aug 5, 2020, at 8:54 AM, Coleen Phillimore <coleen.phillimore at oracle.com> wrote:
> Thank you for the analysis why _last_sweep is a problem.  I am not happy to check in something with UB but I'd like to not try to fix a different problem with this patch.

Understood.

>  Since there are currently no 32 bit GCs that do concurrent weak reference processing, I've filed another bug to have this fixed: https://bugs.openjdk.java.net/browse/JDK-8251179

OK.  I think Markus plans to deal with that quickly, once your change is in.

So your change looks good to me.