6992189: G1: inconsistent base used in sparse rem set iterator
Summary: The remembered set iterator for sparse tables incorrectly assumes that index 0 corresponds to the bottom of the heap, not address 0 as it is the case.
Reviewed-by: ysr, jmasa
6990359: G1: don't push a stolen entry on the taskqueue, deal with it directly
Summary: When an entry is stolen, don't push it on the task queue but process it directly.
Reviewed-by: iveresov, ysr, jcoomes