The previous vertical padding halving had no visible effect: the
inactive button's own vertical padding was hardcoded to 16, which
already exceeded content height + 2*_outerPaddingV at the old value
(5) and kept doing so at the new one (2.5) - so it stayed the tallest
row element regardless of _outerPaddingV, and the header's total
height never actually shrank. Deriving it as 6 + _outerPaddingV
(mirroring the active button's own 6 plus the wrap it would get)
keeps it exactly as tall as the active button and the middle content,
so changes to _outerPaddingV now actually propagate.
Constantin Leue
ae48a0deba