RFR (XS): 8179677: Let G1Remset::_conc_refined_cards only count number of cards concurrently refined

[Thomas Schatzl]

Hi all,

  can I have reviews for this small change that
makes G1Remset::_conc_refined_cards only count the number of
concurrently refined cards (+ some trivial renaming of the variable)?

The reason is that I plan to add the number of refined cards during gc
as separately soon. This has been suggested earlier in some internal
discussion, and I agree.

CR:
https://bugs.openjdk.java.net/browse/JDK-8179677
Webrev:
http://cr.openjdk.java.net/~tschatzl/8179677/webrev.1/
Testing:
jprt

Thanks,
  Thomas