▶ ERROR [expected OK] /fetch/fetch-later/quota/same-origin-iframe/empty-payload.tentative.https.window.html
  │   → Unhandled rejection: iframe[src=https://web-platform.test:8443/fetch/fetch-later/resources/fetch-later.html?url=%252Ffetch%252Ffetch-later%252Fresources%252Fset_beacon.py%253Fuuid%253D9be953e2-9955-4745-ba37-931a64b11b82&activateAfter=0&method=POST&bodyType=FormData&bodySize=0] threw ReferenceError, expected no error
  │ 
  │ FetchLaterExpectationError@https://web-platform.test:8443/fetch/fetch-later/resources/fetch-later-helper.js:344:5
  │ run@https://web-platform.test:8443/fetch/fetch-later/resources/fetch-later-helper.js:391:15
  └ handler@https://web-platform.test:8443/fetch/fetch-later/resources/fetch-later-helper.js:497:20