RFR: Cherry-pick: 8213489: GC/C2 abstraction for Compile::final_graph_reshaping() plus Shenandoah parts

[Aleksey Shipilev]

On 11/12/2018 11:42 PM, Roman Kennke wrote:
> In preparation and to ease next upstream merge, I'd like to cherry-pick
> "8213489: GC/C2 abstraction for Compile::final_graph_reshaping()" and
> the corresponding Shenandoah parts.
> 
> This is a particularily nasty one to merge because it doesn't actually
> conflict and would compile just fine, yet leave all the Shenandoah parts
> in shared code.
> 
> http://cr.openjdk.java.net/~rkennke/JDK-8213489-shenandoah/webrev.00/

OK.

-Aleksey