[css-properties-values-api] Allow @property in shadow trees

[andruud]

No description provided.

[andruud]

@tabatkins: A question in the form of a PR: did you intend to lift this restriction in ed18327 ?

It seems odd to have good rationale for a certain ShadowDOM behavior (2.8), and then not allow @property in shadow trees.

[tabatkins]

...yes, I did intend to lift the restriction in that other commit. Thanks for the catch. ^_^

[foolip]

Looks like https://github.com/web-platform-tests/wpt/blob/master/css/css-properties-values-api/at-property-shadow.html will need to updated to match what the spec says.

[emilio]

@andruud @tabatkins @astearns: Was dis discussed in the working group / was there a resolution on this?

It seems weird that we "leak" property definitions from shadow roots into the global scope. But also the ordering of the registrations etc needs to be defined. I don't think right now we have a dependency between the order of stylesheets inside vs. outside a shadow tree.

[andruud]

ordering of the registrations etc needs to be defined

Indeed, I've also wondered about this.

[astearns]

@emilio I think this is a relevant resolution (but a bit vague) w3c/csswg-drafts#1995 (comment)

[emilio]

@astearns there's no mention of @property there, nor in https://drafts.csswg.org/css-scoping-1/#shadow-names which was the section that discussion was about?

[astearns]

@emilio more discussion of @property: #939