Test new WebIDL mixin syntax

[tobie]

WebIDL recently introduced dedicated syntax for mixins.

This syntax replaces the [NoInterfaceObject] extended attribute and implements statement which have been deprecated (except for a few legacy uses cases explicitely mentioned in the spec).

You can read more about it here.

Todo:

• Remove any tests for implements statements.
• Remove any tests for non-legacy usage of the [NoInterfaceObject] extended attribute.
• Add tests for includes statements and interface mixins.
• Test [SecureContext] for interface mixin members.
• Test [Exposed] for interface mixin members.

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Tracked in: whatwg/webidl#472 | Original pull-request: whatwg/webidl#433

[marcoscaceres]

@tobie, @foolip, I saw recently that IDL from specs was being periodically automagically imported into the appropriate files in the /interfaces/ folder.

Given all specs were fixed to no longer use implements (except this one, which hopefully will be fixed soon!), does that mean all of the above tasks are implicitly done also?

[marcoscaceres]

fixed link above.

[tobie]

@foolip knows the details of this. I don’t.

[foolip]

That's an effort that @lukebjerring has been driving, but is now in a bit of a hiatus as we figure out what the source of IDL snippets should really be, see w3c/webref#3.

[marcoscaceres]

ok great! will wait for an update from @lukebjerring.

[lukebjerring]

I can basically try and sync all of the pending PRs up to current crawled spec's state, and we can go from there for updating implements offenders. Will post when I've taken some action.

[marcoscaceres]

Sounds great, @lukebjerring. let us know if we can help in some way.

[lukebjerring]

Update: It looks like the add_dependency_idls function isn't detecting mixin items correctly.
When Foo implements Bar and we're defining or extending Bar, Foo should be added as untested.

e.g.
partial interface mixin WindowOrWorkerGlobalScope {
[Replaceable] readonly attribute Performance performance;
};

Should be adding Window and WorkerGlobalScope which include the mixin.

EDIT: Addressed by #12165