RFR(S): 7200261: G1: Liveness counting inconsistencies during marking verification

[John Cuthbertson]

Hi Everyone,

Can I have a couple of volunteers look over the fix for this CR? The 
webrev can be found at: http://cr.openjdk.java.net/~johnc/7200261/webrev.0/

Summary:
The clipping in the code that sets the bits for a range of cards in the 
"expected" card bitmap that we check the liveness accounting data 
against was incorrect. This could lead to spurious verification 
failures. In addition to fixing the clipping, I've upleveled this 
routine and moved it into ConcurrentMark and now use it to generate the 
real liveness data.

Testing:
The failing test cases with marking verification; jprt.

Thanks,

JohnC