Minor syntactic questions on vertical-align now that it's a multi-valued shorthand:

• Should we allow the auto value of baseline-source in the shorthand?
  It's not clear what it refers to, is not useful (it's the default behavior), and is left out of serialization anyway... and if at some point we have some longhand that has a meaningful auto value, it would prevent being able to specify that. So I've a slight preference to keep it out of the shorthand.

• What's the best canonical ordering of the values?
  Seems like baseline-source should go first since English has that preference built into its grammar, but is there a preferred order for alignment-baseline vs. baseline-shift? (I'm leaning towards making alignment-baseline go first.)

• css-align restricts the position of first | last to right before the baseline keyword. Should we similarly restrict it in vertical-align? Or let it be reordered since it's parseable either way?