HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert_heap_not_locked_and_not_at_safepoint();
      assert(!isHumongous(word_size), "we do not allow humongous TLABs");

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

      unsigned int dummy_gc_count_before;
      return attempt_allocation(word_size, &dummy_gc_count_before);
    }