RFR (S): JDK-8057910: G1: BOT verification should not pass top

[Bengt Rutisson]

Hi all,

Can I have a couple of reviews for this fix?

http://cr.openjdk.java.net/~brutisso/8057910/webrev.00/

https://bugs.openjdk.java.net/browse/JDK-8057910


After the fix for JDK-8025564 the BOT verification may pass the end for 
the reserved space. The reason is this code in G1BlockOffsetArray::verify():

   size_t start_card = _array->index_for(gsp()->bottom());
   size_t end_card = _array->index_for(gsp()->top());

The end_card should not be based on top() but on "top() - 1" to make 
sure we are inside the heap region and thus inside the reserved space.

Testing:
- Ad hoc aurora tests simulating nightly testing. The current bug failed 
a lot in the nightly testing.
- JPRT

Thanks,
Bengt