RFR: Avoid evacuating filler objects in Shenandoah

[Roman Kennke]

Hi Zhengyu,

> 
> Webrev:
> http://cr.openjdk.java.net/~zgu/shenandoah/sh_filler/webrev.00/index.html
> 
> Thanks,
> 
> -Zhengyu

Is the motivation for this change that we can check that the objects we
are evacuating are not filler objects?

I don't really understand what you mean by:


> Using fake filler array klass seems to have less side-effects,
> especially on upstream collectors.
>
> The drawback is that, we still evacuate small object fillers, since fake
> filler object is not easy.
>

I'm probably missing some context ;-)

Roman