[css-grid] Refactor positioned children code
Created attachment 275101 [details] Patch
This is a port of: https://codereview.chromium.org/1838173002/
Comment on attachment 275101 [details] Patch Clearing flags on attachment: 275101 Committed r198834: <http://trac.webkit.org/changeset/198834>
All reviewed patches have been landed. Closing bug.