Summary: When G1 is run with -XX:-G1DeferredRSUpdate, the VM crashes because of wrong initialization order of member variables. The change makes the initalization explicit, not relying on initialization order any more.
Reviewed-by: brutisso, mgerdin

Summary: After JDK-8035400 there were several opportunities to fix the visibility of several members of the G1ParScanThreadState class.
Reviewed-by: brutisso, mgerdin

Summary: Extract the G1ParScanThreadState class from G1CollectedHeap.?pp into its own files.
Reviewed-by: brutisso, mgerdin