RFR: Refactor ShConcThread dispatch

[Roman Kennke]

Am 25.08.2017 um 17:14 schrieb Aleksey Shipilev:
> http://cr.openjdk.java.net/~shade/shenandoah/concthread-dispatch-refactor/webrev.01/
> 
> A few improvements:
>  a) Skip updating the counters if no GC had happened;
>  b) Avoid attempting to shrink heap on every tick -- avoids taking ShHeapLock every 10ms;
>  c) Code style
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 

Good!