The CSSOM spec makes multiple references to the concept of "in canonical order", as meaning a canonical order for the longhands of a shorthand property.  But it doesn't define this term anywhere.

Similarly, we've added a "Canonical order" line to the propdef tables, but I thought that the "Canonical order" in the propdef tables was about defining value serialization, even for longhand properties, rather than an order for the subproperties of a shorthand.  If this is the case, then this definition should be used somewhere.

Either way, the spec should have something useful to link the term "Canonical order" in the propdef tables to, per https://github.com/tabatkins/bikeshed/issues/617