[observe.html]
  expected: TIMEOUT
  [guard]
    expected: NOTRUN

  [test8: simple content-box observation]
    expected: [PASS, FAIL]

  [test9: simple content-box observation but keep border-box size unchanged]
    expected: [PASS, FAIL]

  [test10: simple border-box observation]
    expected: [PASS, FAIL]