when the containing block of a out-of-flow positioned element establishes an inline formatting context <span style="position: relative"><span style="position: absolute; top: 10px; left: 10px;">foobar</span></span>
Created attachment 337617 [details] Patch
Committed r230484: <https://trac.webkit.org/changeset/230484>
<rdar://problem/39318403>