According to the latest spec the last 3 parameters should be optional.

I think the correct behavior should be: 

1) If timeline is not provided  we should default to default document timeline.
2) If options is not provided, assume there is not options. We currently don't
even support "options" so it should definitely be optional. (Perhaps even we
should throw when it is actually specified?)

Note that Effect may also be allowed empty by we don't currently support
unprovided effects. Unlike timeline and options, I don't see why someone may
even try to no provide an effect so it is not as important to fix that one yet.


``` [Constructor (DOMString animatorName,
              optional (AnimationEffectReadOnly or sequence)? effects = null,
              optional AnimationTimeline? timeline, optional any options)]
interface WorkletAnimation : Animation {
        readonly attribute DOMString animatorName;
};

```

[1] https://wicg.github.io/animation-worklet/#creating-worklet-animation