RFR: jdk11: guard shared code with UseShenandoahGC

[Aleksey Shipilev]

On 10/17/2018 05:14 PM, Roland Westrelin wrote:
> http://cr.openjdk.java.net/~roland/shenandoah/jdk11-UseShenandoahGC/webrev.00/
> 
> Some missing UseShenandoahGC to guard shared code changes.

These look good. We'll need to glance over webrev after this patch lands.

> I also propose we drop the changes related to the register doubling stuff from 11.

Not sure, why? Can we "just" protect them with UseShenandoahGC as well?

-Aleksey