[resize-observer] Missing 2nd argument from ResizeObservation constructor

[Loirooriol]

From https://drafts.csswg.org/resize-observer/#resizeobservation

interface ResizeObservation {
    constructor(Element target);
    readonly attribute Element target;
    readonly attribute ResizeObserverBoxOptions observedBox;
    readonly attribute FrozenArray<ResizeObserverSize> lastReportedSizes;
};

But the constructor actually has an optional observedBox parameter:

new ResizeObservation(target, observedBox)

1. Let this be a new ResizeObservation object
2. Set this internal target slot to target
3. Set this internal observedBox slot to observedBox
4. Set this internal lastReportedSizes slot to [(0,0)]