If you use "span" alone to reference a grid line it should be considered an invalid declaration (e.g. "grid-column: span;").
This is a port from a Blink patch: https://codereview.chromium.org/1970573004/
Created attachment 278708 [details]
Comment on attachment 278708 [details]
Clearing flags on attachment: 278708
Committed r200755: <http://trac.webkit.org/changeset/200755>
All reviewed patches have been landed. Closing bug.