RFR (S): 8135200: Add White Box method that enumerates G1 old regions with less than specified liveness and collects statistics.

[Kirill Zhaldybin]

Hi!

Could you please review a patch for JDK-8135200?

I added White Box method that enumerates G1 old regions with less than 
specified liveness and collects statistics.

CR: https://bugs.openjdk.java.net/browse/JDK-8135200

Webrev:
http://cr.openjdk.java.net/~kzhaldyb/webrevs/JDK-8135200/webrev.00/
hotspot: 
http://cr.openjdk.java.net/~kzhaldyb/webrevs/JDK-8135200/hotspot/webrev.00/

Thank you.

Regards, Kirill