RFR: 8227086: Use AS_NO_KEEPALIVE loads in HeapDumper

[Kim Barrett]

> On Jul 2, 2019, at 9:53 AM, Stefan Karlsson <stefan.karlsson at oracle.com> wrote:
> 
> Hi all,
> 
> Please review this patch to read objects with AS_NO_KEEPALIVE in the HeapDumper.
> 
> http://cr.openjdk.java.net/~stefank/8227086/webrev.01/
> https://bugs.openjdk.java.net/browse/JDK-8227086
> 
> Found this while running some extra verification code through our barriers. This is one place where we use ON_UNKNOWN_OOP_REF without AS_NO_KEEPALIVE. The current code isn't wrong, but we could just as well use the more light-weight load barrier here.
> 
> Tested with tier 1-7
> 
> Thanks,
> StefanK

Looks good.