RFR: Remove ZStatReference's dropped statistics count

[Stefan Karlsson]

Looks good.

StefanK

On 2018-03-05 15:31, Per Liden wrote:
> This patch removes the "dropped" count from the reference processor 
> and instead tracks "discovered" events, so that we have the more 
> natural "encountered", "discovered" and "enqueued" counters. Dropped 
> could be calculated from discovered - enqueued if needed in the future.
>
> http://cr.openjdk.java.net/~pliden/zgc/remove_zstat_reference_dropped/webrev.0/ 
>
>
> /Per