Prioi to JDK-8342382, card-mark must be after store so that refine threads can see the new stored value on performing refinement. Hence the following method.

  virtual bool card_mark_must_follow_store() const {
    return true;
  }

Nowadays, refine threads would handshake with mutators (`G1ConcurrentRefineSweepState::swap_java_threads_ct`) so that those stores are visible to refine threads.