The CSS Grid Layout spec states the following to deal with 'auto' values for the margin properties. http://dev.w3.org/csswg/css-grid/#auto-margins
Created attachment 256095 [details] Patch
Created attachment 256112 [details] Patch
Comment on attachment 256112 [details] Patch Clearing flags on attachment: 256112 Committed r186682: <http://trac.webkit.org/changeset/186682>
All reviewed patches have been landed. Closing bug.