Bug 96143 added code to avoid autosizing text in constrained height elements. Working out whether the height of text is constrained when the containing block has a perpendicular writing mode is tricky (especially since WebKit itself currently gets this wrong in several places), so this was left as a FIXME, which this bug intends to fix.
Any future known conflicts between Text Autosizing and vertical writing modes will also be added to this bug.
Adding two vertical writing mode bugs that block this.
Marking this bug Resolved WontFix because the TEXT_AUTOSIZING feature was removed in <https://trac.webkit.org/changeset/206119> (bug #162167). See bug 84186, comment 32 for more details.