_saved_mark_word and its accessor is used in Serial young-gc as kind of mark during scavenging. They don't really belong to ContiguousSpace.
Move _saved_mark_word and related code to Serial young-gc. (Maybe `DefNewGeneration` and `TenuredGeneration`, or any other more sensible locations.)
Move _saved_mark_word and related code to Serial young-gc. (Maybe `DefNewGeneration` and `TenuredGeneration`, or any other more sensible locations.)