This is a testharness.js-based test.
[FAIL] <video controls=""></video> has a shadow tree with no slots
  assert_true: child should be outside the flat tree expected true got false
[FAIL] <video></video> has a shadow tree with no slots
  assert_true: child should be outside the flat tree expected true got false
[FAIL] <audio></audio> has a shadow tree with no slots
  assert_true: child should be outside the flat tree expected true got false
[FAIL] <audio controls=""></audio> has a shadow tree with no slots
  assert_true: child should be outside the flat tree expected true got false
Harness: the test ran to completion.