[scroll-animations-1] should ViewTimelineOptions.subject be required?

[graouts]

While reviewing an early patch for ViewTimeline and ViewTimelineOptions in WebKit, a question about the spec came up:

I suspect the spec intended this dictionary member to be marked as required since it is not nullable and the corresponding attribute on the interface is not nullable either. May be worth filing an issue against the spec.

Should the ViewTimelineOptions be specified as follows?

dictionary ViewTimelineOptions {
  required Element subject;
  ScrollAxis axis = "block";
  (DOMString or sequence<(CSSNumericValue or CSSKeywordValue)>) inset = "auto";
};

[birtles]

I'm not familiar with ViewTimeline I'm afraid. Removing myself as reviewer.