[web-animations-1] Mapping between IDL and resolved/unresolved time values should be defined

Consider the setter for https://drafts.csswg.org/web-animations/#dom-animation-currenttime

This takes a nullable double. It passes this nullable double to https://drafts.csswg.org/web-animations/#set-the-current-time which then passes it to https://drafts.csswg.org/web-animations/#silently-set-the-current-time

This then talks about whether time values are "resolved" or not. But nothing defines what that actually means in this case. Presumably the intent is that IDL null map to the "unresolved" state, but that needs to be defined. Perhaps what's needed here is a mapping from nullable double values to time values (and vice versa; it's not clear to me what happens with getters in this specification that are supposed to return a nullable double if a time value is not representable as a double, for example).

Read the Web Animations specification sections for the currentTime setter, “set the current time,” and “silently set the current time.” Determine how nullable IDL doubles map to resolved and unresolved time values, including getter conversion, and consider the issue complete when both directions are defined consistently.