.classList.add('vertical');
      // The inline containment on #c2 now applies to the vertical axis.
      // [cqi, cqb] still corresponds to [cqh, cqw], but we now expect
      // cqh to resolve against #c2, and cqw to resolve against #c1.
      assert_unit_equals(child, '10cqw', '50px');
      assert_unit_equals(child, '10cqi', '20px');
      assert_unit_equals(child, '10cqh', '20px');
      assert_unit_equals(child, '10cqb', '50px');

    } finally {
      for (let c of [c1, c2, c3, c4, child])
        c