RFR (S): 8223162: Increase ergonomics for Sparse PRT entry sizing

[Kim Barrett]

> On May 24, 2019, at 9:24 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> […]CR:
> https://bugs.openjdk.java.net/browse/JDK-8223162
> Webrev:
> http://cr.openjdk.java.net/~tschatzl/8223162/webrev/
> Testing:
> lots of remembered set size measurements on lots of applications, some
> hs-tier1-5 runs together with other changes.
> 
> Thanks,
>  Thomas

src/hotspot/share/gc/g1/sparsePRT.hpp
 241   enum SomeAdditionalPrivateConstants {
 242     InitialCapacity = 8
 243   };

Since you are touching it, consider making InitialCapacity a static
const size_t rather than an enumerator, so it has a consistent type
across platforms.

Other than that, looks good.  I don't need a new review if you change
how InitialCapacity is defined.