RFR: Update counters on slow-path more rarely

[Zhengyu Gu]

Okay.

-Zhengyu

On 08/30/2017 01:06 PM, Aleksey Shipilev wrote:
> Running with -UseTLAB, thus stressing shared allocations, is slow because we update the counters
> even for the minuscule shared allocations. It makes sense to do this only when new region is claimed
> during shared alloc.
> 
> Fix:
>    http://cr.openjdk.java.net/~shade/shenandoah/alloc-lazier-counters/webrev.01/
> 
> Also removes some superfluous asserts and refactors a bit
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
>