[cssom-1, css-cascade-5] Add adoptedStyleSheets using ObservableArray

[mfreed7]

[cssom-1, css-cascade-5] Add adoptedStyleSheets using ObservableArray.

Some things I need input on:

1. See this discussion. I added a single list item to the Cascade-5 text to reference the new "final CSS style sheets" concept I added in CSSOM-1. We might (?) want to instead change the styleSheets property to explicitly exclude the contents of adoptedStyleSheets, and fold "final CSS style sheets" back into "document or shadow root CSS style sheets".
2. I can't seem to get the "link magic" working between cssom-1 and css-cascade-5. I tried various permutations of <a for=foobar>concept name</a> but nothing seemed to please bikeshed. So I resorted to <a href=>. Help appreciated.

Credit to @domenic for a draft of this PR.

@emilio

Closes WICG/construct-stylesheets#118, Closes WICG/construct-stylesheets#93

[dbaron]

I can't seem to get the "link magic" working between cssom-1 and css-cascade-5. I tried various permutations of concept name but nothing seemed to please bikeshed. So I resorted to <a href=>. Help appreciated.

I believe bikeshed's only mode of operation is processing one spec at a time, relative to the published (editor's draft or TR) versions of other specs. I don't think there's a way to process multiple drafts at once to test whether cross-draft linking changes that require edits to multiple drafts will work. I think the thing to do is look at what generally works elsewhere, do that, and check it afterwards.

[emilio]

Yeah, the contents look good to me, but I'm pretty sure the linking needs work. Maybe it's worth landing this in different PRs assuming there's no circular dependency?

[mfreed7]

Yeah, the contents look good to me, but I'm pretty sure the linking needs work. Maybe it's worth landing this in different PRs assuming there's no circular dependency?

Thanks for the comments here. I'm happy to land the change to css-cascade-5 in a later PR, but see my comment above. I can't seem to get even the internal references to work. I think something about the <code> block or something, but nothing I tried worked. I'm sure it's easy and I'm just missing it.

[mfreed7]

I left the HREF here for now, and I'll land a followup CL converting it to a bikeshed link after this lands, if that's ok with you.

[domenic]

Suggested change

	<li>Style sheets are ordered as in <a href="https://www.w3.org/TR/cssom-1/#documentorshadowroot-final-css-style-sheets">final CSS style sheets</a>.
	<li>Style sheets are ordered as in <a href="https://drafts.csswg.org/cssom/#documentorshadowroot-final-css-style-sheets">final CSS style sheets</a>.

since the TR URL there is stuck in 2016.

[mfreed7]

Oops, better, thanks.

[mfreed7]

Yeah, the contents look good to me, but I'm pretty sure the linking needs work. Maybe it's worth landing this in different PRs assuming there's no circular dependency?

Ok, I think the linking should be pretty clean now. What do you think?

[emilio]

This looks great, what do you think about the nit below? Either way seems fine to me.

[mfreed7]

Thanks for the review/comments!