In claim-with-redirect.https.html, UPDATE_IFRAME_URL doesn't seem to have anything to do with redirects and claim. It looks like we're just making an iframe in a different origin and checking that that iframe can call update().

This comes from discussions in the CL https://chromium-review.googlesource.com/c/chromium/src/+/1056755, is a tracker for us to make clear the test logic.