[15] RFR 8242375: Shenandoah: Remove ShenandoahHeuristic::record_gc_start/end methods

[Roman Kennke]

Ok, looks good!

Thank you!
Roman

> Please review this patch to remove
> ShenandoahHeuristic::record_gc_start()/end() methods, they have no
> implementation and are called from wrong places.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8242375
> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8242375/webrev.00/index.html
> 
> 
> Test:
>   hotspot_gc_shenandoah
> 
> 
> Thanks,
> 
> -Zhengyu
>