Guess it does not really make too much sense to have negative width (even if it breaks the 'margin-left' + 'border-left-width' + 'padding-left' + 'width' + 'padding-right' + 'border-right-width' + 'margin-right' = width of containing block constraint)
Created attachment 359268 [details] Patch
Created attachment 359328 [details] Patch
Comment on attachment 359328 [details] Patch Clearing flags on attachment: 359328 Committed r240093: <https://trac.webkit.org/changeset/240093>
All reviewed patches have been landed. Closing bug.
<rdar://problem/47333936>