[relevant-mutations.html]
  type: testharness
  [ancestor picture; previous sibling source inserted]
    expected: FAIL

  [picture is inserted; img has previous sibling source]
    expected: FAIL

  [crossorigin state not changed: anonymous to foobar]
    expected: FAIL

  [crossorigin state not changed: empty to anonymous]
    expected: FAIL

  [ancestor picture; previous sibling source removed]
    expected: FAIL

  [crossorigin state not changed: use-credentials to USE-CREDENTIALS]
    expected: FAIL

  [picture is inserted; img has following sibling source]
    expected: FAIL

  [picture is inserted; img has srcset]
    expected: FAIL

  [picture is inserted; img has src]
    expected: FAIL

  [sizes is set to same value]
    expected: FAIL