Set iframe lazy load resumption steps to null on navigation

[zcorpan]

When an iframe element is navigated, the lazy-loading mechanism should not navigate it again.

Fixes #10213.

• [x] At least two implementers are interested (and none opposed):
  • Gecko
  • Chromium (already implemented)
• [x] Tests are written and can be reviewed and commented upon at:
  • https://github.com/web-platform-tests/wpt/pull/45650
• [x] Implementation bugs are filed:
  • Chromium: https://issues.chromium.org/u/1/issues/334720105
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1882670
  • WebKit: https://bugs.webkit.org/show_bug.cgi?id=272677
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): …
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• [x] MDN issue is filed: N/A
• [x] The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/browsing-the-web.html ( diff ) /urls-and-fetching.html ( diff )

[domfarolino]

So spec-wise this looks fine, but I think there is an outstanding question about what other non-Chromium browsers do in this case, and if we have any existing WPTs for this scenario (https://github.com/whatwg/html/issues/10213#issuecomment-2025861685). I presume you're still investigating that side of things?

[zcorpan]

Tests at https://github.com/web-platform-tests/wpt/pull/45650