[CustomElementRegistry-getName.tentative.html]
  [customElements.getName must return null when the registry does not contain an entry with the given constructor]
    expected: FAIL

  [customElements.getName returns the name of the entry with the given constructor when there is a matching entry.]
    expected: FAIL

  [customElements.getName returns the name of the entry with the given customized built in constructor when there is a matching entry.]
    expected: FAIL