RFR: 8140602: Split other time calculation into methods in G1CollectorPolicy

[Erik Helin]

Hi all,

this small patch extracts the other time calculations in
G1CollectorPolicy into separate methods. The code becomes shorter and
easier to read.

Enhancement:
https://bugs.openjdk.java.net/browse/JDK-8140602

Webrev:
http://cr.openjdk.java.net/~ehelin/8140602/webrev.00/

Thanks,
Erik