RFR(S) 8220546: Shenandoah Reports timing details for weak root processing

[Roman Kennke]

Hi Zhengyu,

cool stuff!

- I find the naming/style weird and out of place: 
WeakProcessorTimingToShenandoahTiming(..) can we stick to 
weak_processor_timing_... style?
- I suppose it is intended and ok to have all threads do this:
+    _processed_weak_roots = true;

Other than that, ok!

Roman

> Please review this patch that catches WeakProcessor's timings into 
> shenandoah's timings.
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8220546
> Webrev: http://cr.openjdk.java.net/~zgu/JDK-8220546/webrev.00/
> 
> Sample output: http://cr.openjdk.java.net/~zgu/JDK-8220546/par_timings.log
> 
> Test:
>    hotspot_gc_sheanndoah (fastdebug and release)
> 
> 
> Thanks,
> 
> -Zhengyu
>