Add NavigateEvent.sourceElement

[noamr]

The sourceElement of the navigate event is either the clicked link, the submitter button, or the submitted form if there was no submitter button.

See https://github.com/WICG/navigation-api?tab=readme-ov-file#navigation-monitoring-and-interception

• At least two implementers are interested (and none opposed):
  • Chromium (implementing)
  • Awaiting Gecko position: Navigation API: sourceElement mozilla/standards-positions#1154
  • Awaiting WebKit position Navigation API: sourceElement WebKit/standards-positions#441
• Tests are written and can be reviewed and commented upon at:
  • https://wpt.fyi/results/navigation-api/navigate-event?label=master&label=experimental&aligned&q=navigate-event
• Implementation bugs are filed:
  • Chromium: https://issues.chromium.org/issues/40281924
  • Gecko: https://bugzilla.mozilla.org/show_bug.cgi?id=1941729
  • WebKit: https://bugs.webkit.org/show_bug.cgi?id=285977
  • Deno (only for timers, structured clone, base64 utils, channel messaging, module resolution, web workers, and web storage): N/A
  • Node.js (only for timers, structured clone, base64 utils, channel messaging, and module resolution): …
• Corresponding HTML AAM & ARIA in HTML issues & PRs: N/A, this does not affect HTML components, but rather a JS API.
• MDN issue is filed: …
• 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 )
/form-control-infrastructure.html ( diff )
/links.html ( diff )
/nav-history-apis.html ( diff )

[annevk]

cc @rwlbuis

[domenic]

Beautiful! I'm thankful we didn't have to thread this through too many layers 😅

[domenic]

Tests are written and can be reviewed and commented upon at:

I think we should revert web-platform-tests/wpt#46072 too