RFR (S): 8250628: ZGC: `fixup_partial_loads` was removed, but still are referenced

[Kim Barrett]

> On Jul 29, 2020, at 8:19 AM, Albert Yang <albert.m.yang at oracle.com> wrote:
> 
> Hi,
> 
> https://bugs.openjdk.java.net/browse/JDK-8250628
> 
> http://cr.openjdk.java.net/~lkorinth/albert/8250628/0/
> 
> Case 2&3 can be removed, since all roots will go through the load barrier before a safepoint. To be safe, I have tried setting them to true via `FLAG_SET_DEFAULT(_, true);`, and no failures are observed for hotspot-gc.
> 
> Tested: hotspot-gc
> 
> /Albert

The change looks okay, but I'm not sure about the testing.

VerifyBeforeIteration is (only) used by jvmti heap iteration
functions, and I don't think the hotspot_gc test group includes any
jvmti tests.