RFR: Excessive asserts in marked_object_iterate

[Zhengyu Gu]

Looks good.

-Zhengyu

On 03/19/2018 07:41 AM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/asserts-marked-excess/webrev.01/
> 
> We don't need five asserts, when we can have only two:
>    - is_null is getting implicitly checked with is_oop
>    - is_in is checked implicitly with is_oop
>    - (bitmap == complete) is implied by current calling code
> 
> Makes fastdebug builds a bit faster.
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
>