Add a non-normative note stating elements in shadow trees aren't exposed as named properties

[rniwa]

I think the following text in the spec

Window object named properties [HTML] must access the nodes in the document tree.

is meant to clarify that elements in shadow trees aren't exposed as named properties on Window.

Perhaps we want to add an informative note stating that explicitly.

[annevk]

I don't understand this feedback.

This applies to a huge number of APIs. It wouldn't make sense to enumerate them all. Why this one?

[rniwa]

That too. It's a bit strange to explicitly call out this one. Does DOM spec says only nodes that are in the document (i.e. its root ancestor node is the document) are exposed as named properties?

[annevk]

It seems pretty clear about "active document": https://html.spec.whatwg.org/multipage/browsers.html#named-access-on-the-window-object

The only curious thing might be whether an <iframe> inside a shadow tree creates a nested browsing context or not. And if not, what does it create?

[rniwa]

It should create a nested browsing context, right? I don't think there is anything special about iframes inside shadow trees.

[annevk]

Well, if it creates a nested browsing context (and that requires a changed definition of "is in a document" iirc), it would be exposed on Window, unless we change that definition somehow.

[hayatoito]

As the short time fix, we should change the nodes to anything (or something?) so that it also excludes browsing context in shadow trees?
The intention is "Don't leak anything in shadow trees via Window". However, I'm afraid that there is an exception we are missing.

[annevk]

This is a duplicate of #145 I think.