[css-typed-om-1] liveness behavior not very clear for the set of properties on StylePropertyMaps

[bzbarsky]

https://drafts.css-houdini.org/css-typed-om-1/#declared-stylepropertymap-objects says things like:

When constructed, the map entries for declared StylePropertyMap objects is initialized to contain an entry for each property with a valid value inside the CSSStyleRule or inline style that the object represents, in the same order as the CSSStyleRule or inline style.

Nothing in this spec defines how that map entries can change after that point (apart from API calls on it). What happens if the values of the properties involved changes? What happens if the set of properties involved changes? Nothing seems to define the behavior.