[css-view-transitions-2] Allow empty :active-view-transition() ?

[fantasai]

In general, if there's reasonable default behavior, we allow omitting arguments, so... should :active-view-transition() be equivalent to :active-view-transition(*)?

[ydaniv]

Basically with empty params it reads as a transition with zero types, unlike * which reads as any types. I guess there's a difference. It could be used as selecting the default transition with zero specified types, if that makes sense.

[nt1m]

I would prefer allowing :active-view-transition over :active-view-transition() (as an alias to :active-view-transition(*)). The former reads "There is an active view transition" whereas the latter reads as "There is an active view transition with empty arguments". So the former makes more sense as a short syntax for :active-view-transition(*)

[astearns]

We resolved in #9972 (comment) to have two versions, one which omits arguments and one that must take a type argument