8227719: G1 Pending cards estimation too conservative in cost prediction Summary: Instead of using a coarse prediction for the log buffers, accumulate the actual number directly. Reviewed-by: kbarrett, sangheki

8226913: Scale cards per chunk used during heap root scanning with region size Summary: Scale cards per chunk based on heap size to decrease constant overhead with heap root scanning data structure initialization Reviewed-by: kbarrett, sangheki