RFR (XS): 8184452: Add bounds checking for FromCardCache

[Thomas Schatzl]

Hi all,

  can I have reviews for this change that adds asserts/bounds checking
to the FromCardCache methods?

This helped me a lot to find crashes in some upcoming change, and I
think it is useful to have. If you think it is not worth the trouble,
feel free to tell me and I will retract the change.

CR:
https://bugs.openjdk.java.net/browse/JDK-8184452
Webrev:
http://cr.openjdk.java.net/~tschatzl/8184452/webrev/
Testing:
jprt

Thanks,
  Thomas