In what APIs will DOMQuad and DOMPoint be used?

For example, I see the geometry-interfaces spec lists those interfaces, but which new APIs will actually be built around those interfaces, which APIs will return those things?

For example, there’s Firefox’s getBoxQuads method that returns a DOMQuad, but I don’t see that spec’d anywhere.

What things (if any) are spec’d and will return or consume DOMQuads?

getBoxQuads is defined in CSSOM View