[css-typed-om] CSSUnparsedValue constructor behaviour if arguments are not alternating

[darrnshn]

In the wording for the tokens internal slot of CSSUnparsedValue, it says that tokens is "a list of alternating DOMString and CSSVariableReferenceValue objects". What happens if a CSSUnparsedValue was created with non-alternating tokens? e.g.

new CSSUnparsedValue('foo', 'bar');

[tabatkins]

That statement is just wrong in the first place - I think --foo:var(bar)var(baz); would have two variables references in a row, without a string in the middle. (Theoretically we could put an empty string there, but why?) I should remove it.

[shans]

I don't think I ever intended it to mean strictly alternating. The sense was that you could alternate back and forth between the two types in a single list (as opposed to either having a list of one or a list of the other).

We definitely should reword to make this less confusing, but I think it'd be good to retain that sense somehow.