RFR Backport: 8255269: Unsigned overflow in g1Policy.cpp

[Kemper, William]

?Please review and consider backporting the fix for JDK-8255269 to jdk8u.


Original bug is here: https://bugs.openjdk.java.net/browse/JDK-8255269

Webrev for jdk8u: http://cr.openjdk.java.net/~phh/8255269/webrev.8u.hotspot.01/


I ran the g1 jtreg tests (hotspot/test/gc/g1, hotspot/test/gc_implementation/g1), all 36 tests passed.


Thank you,

William?