while <span style="padding: 100px;"></span> is visually empty (blank) it is not considered empty in when computing the line box geometry.
Created attachment 413000 [details] Patch
Committed r269299: <https://trac.webkit.org/changeset/269299> All reviewed patches have been landed. Closing bug and clearing flags on attachment 413000 [details].
<rdar://problem/70992048>