6861557: G1: assert(top() == bottom() || zfs == Allocated,"Region must be empty, or ...")
Summary: Druing heap shrinking, check for emptiness of a region before modifying its ZF status.
Reviewed-by: tonyp
6880053: assert(alloc_obj->as_CheckCastPP()->type() != TypeInstPtr::NOTNULL)
Summary: Removed second CheckCastPP and use MembarCPUOrder after arraycopy to cloned object.
Reviewed-by: never