RFR (S) 8214972: Uses of klass_holder() except GC need to apply GC barriers

[Erik Osterlund]

Hi Coleen,

Looks good.

Thanks,
/Erik

> On 6 Dec 2018, at 21:47, coleen.phillimore at oracle.com wrote:
> 
> Summary: Fix klass_holder() and make all callers use it, remove holder_phantom().*
> 
> *This removes the confusion about which one to use, except for GC, who has to know.
> 
> open webrev at http://cr.openjdk.java.net/~coleenp/8214972.01/webrev
> bug link https://bugs.openjdk.java.net/browse/JDK-8214972
> 
> Ran tier1-3 tests.
> 
> Thanks,
> Coleen
> **