[11u]: RFR (XS): 8249875: GCC 10 warnings -Wtype-limits with JFR code

[Hohensee, Paul]

Please review this simple backport to 11u. The only conflicts were copyright dates.

Original JBS: https://bugs.openjdk.java.net/browse/JDK-8249875
Original patch: https://hg.openjdk.java.net/jdk/jdk/rev/942b669a4ae3
11u webrev: https://cr.openjdk.java.net/~phh/8249875/webrev.11u.00/

Thanks,
Paul