8219856: Spell out G1CollectorPolicy::is_hetero_heap Reviewed-by: sangheki, kbarrett

8219748: Add and use getter for the timing object in G1 Reviewed-by: shade, kbarrett

8219747: Remove g1_ prefix to g1_remset and g1_policy members in G1CollectedHeap Reviewed-by: shade, sangheki

8219369: Add named constants for iterating ExtRootScan phases Reviewed-by: kbarrett, sangheki