https://www.w3.org/TR/CSS22/visudet.html If the element has 'position: absolute', the containing block is established by the nearest ancestor with a 'position' of 'absolute', 'relative' or 'fixed', in the following way: In the case that the ancestor is an inline element, the containing block is the bounding box around the padding boxes of the first and the last inline boxes generated for that element. In CSS 2.2, if the inline element is split across multiple lines, the containing block is undefined. Otherwise, the containing block is formed by the padding edge of the ancestor.
Created attachment 359133 [details] Patch
Comment on attachment 359133 [details] Patch Clearing flags on attachment: 359133 Committed r239983: <https://trac.webkit.org/changeset/239983>
All reviewed patches have been landed. Closing bug.
<rdar://problem/47283045>