"If line-height computes to normal and either text-edge is leading or this is the root inline box, the font’s line gap metric may also be incorporated into A and D by adding half to each side as half-leading." https://www.w3.org/TR/css-inline-3/#inline-height since we don't have text-edge support yet, it applies to all inline boxes.
Created attachment 418817 [details] Patch
Committed r272118: <https://trac.webkit.org/changeset/272118> All reviewed patches have been landed. Closing bug and clearing flags on attachment 418817 [details].
<rdar://problem/73794661>