RFR: Cleanup obsolete Shenandoah changes in ciInstanceKlass

[Aleksey Shipilev]

On 11/19/18 9:46 PM, Roman Kennke wrote:
> In-fact, I believe it's become possible by a very recent change:
> 
> http://hg.openjdk.java.net/shenandoah/jdk/rev/6082c529aed8

Aha, that explains it. Thanks!

> In other words, it's not backportable, unless you also want to backport
> this other change, and probably a huge tail of other stuff (certainly in
> 8u).

Yeah, I'd keep it from backports for now; we would need to sync up C2 implementations across
backports at some point, and that might be more convenient to test in bulk, and after sh/jdk C2 is
not changing anymore.

-Aleksey