HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
                                                    bool force) {

  {- -------------------------------------------
  (1) G1CollectedHeap::new_mutator_alloc_region() を呼び出すだけ
      ---------------------------------------- -}

      return _g1h->new_mutator_alloc_region(word_size, force);
    }