[iframe-csp-attribute.html]
  [<iframe> has a 'csp' attibute which is an empty string if undefined.]
    expected: FAIL

  [<iframe>'s csp attribute is always a string.]
    expected: FAIL

  [<iframe>'s 'csp content attribute reflects the IDL attribute.]
    expected: FAIL

  [<iframe>'s IDL attribute reflects the DOM attribute.]
    expected: FAIL

