Merge

6888336: G1: avoid explicitly marking and pushing objects in survivor spaces Summary: This change simplifies the interaction between GC and concurrent marking. By disabling survivor spaces during the initial-mark pause we don't need to propagate marks of objects we copy during each GC (since we never need to copy an explicitly marked object). Reviewed-by: johnc, brutisso

7128532: G1: Change default value of G1DefaultMaxNewGenPercent to 80 Reviewed-by: tonyp, jmasa

7125281: G1: heap expansion code is replicated Reviewed-by: brutisso, johnc