"Show the picker" steps never dismisses the picker upon node removal

[domfarolino]

What is the issue with the HTML Standard?

In https://html.spec.whatwg.org/multipage/input.html#show-the-picker%2C-if-applicable, UI gets shown to the user representing the picker for either input or select elements. If those elements get removed from the DOM while the picker is shown (except for type=file apparently), the picker UI gets dismissed immediately in Chrome+Safari, but not Firefox (click the input within 2 seconds of loading the following data: URL):

data:text/html,<input%20id=input%20type=color><script>setTimeout(()%20=>%20{input.remove()},%202000)</script>

Aligning on Chrome/Safari behavior here makes sense to me I think, so we should consider patching up that algorithm to hook into DOM and respond to the removal appropriately by dismissing the picker UI. The solution to this will likely come in the form of semi-handwavy text inside the existing algorithm (although something more procedural could be considered maybe).

Context: I ran into this while working on whatwg/dom#1307.

[annevk]

While not strictly speaking observable to websites (although maybe it is through :open?), it probably makes sense to state something about expectations here.

cc @josepharhar @pxlcoder @nt1m @emilio

[domfarolino]

Does :open exist? I can't find anything about that pseudoselector on MDN.

[annevk]

Hopefully soon: #10126