[css-shapes][css3-backgrounds] No explicit <position> serialization steps in background spec #368
Description
https://drafts.csswg.org/css-shapes/#basic-shape-serialization
https://drafts.csswg.org/css-backgrounds-3/#position
The basic-shape spec mentions:
The values (including the defaults) in ellipse() and circle() serialize to their 2- and 4-value forms only, preferring the 2-value form when it can be expressed without calc(), preferring left and top origins, and preferring 0% over a zero length.
The backgrounds spec does not have serialization steps mentioned at all. Can we assume the same serialization steps?
(This doesn't match existing behavior -- browsers serialize center center as center center instead of 50% 50% for background position)