RFR: Add two missing weak roots sets

[Per Liden]

Looks good!

/Per

On 01/18/2018 02:40 PM, Stefan Karlsson wrote:
> Hi all,
> 
> Please review this patch to add two missing weak roots sets
> 
> http://cr.openjdk.java.net/~stefank/zgc/zMissingWeakRoots/webrev.01/
> 
> The JvmtiExport::weak_oops_do call was moved in the upstream repository, 
> and TRACE_WEAK_OOPS_DO was recently introduced for the Trace API.
> 
> This was found while testing some jdi tests that used the JvmtiTagMap.
> 
> Thanks,
> StefanK