[is-pseudo-containing-sibling-relationship-in-has.html]
  [sibling selector in non-subject enclosed by :is() no longer matching after removal (5)]
    expected:
      if not asan and tsan: [FAIL, PASS]
      if asan: [FAIL, PASS]

  [:nth-child() enclosed by :is() no longer matching after removal (1)]
    expected:
      if not asan and tsan: [FAIL, PASS]
      if asan: [FAIL, PASS]

  [sibling selector in parent selector non-subject position enclosed by :is() no longer matching after removal (1)]
    expected:
      if tsan: [FAIL, PASS]

  [Initially red]
    expected:
      if not asan and tsan: [PASS, FAIL]
      if asan: [PASS, FAIL]