This work around a problem with bounding boxes that are shorter than the center line of the text (the half way point between the font's ascent and descent). Browsers pad boxes shorter than this to be this high, so CHTML has to compensate for that.
This is what was causing CHTML not to exhibit the minimum-height issue in #1706 (closed), so this PR would introduce that bug, and so we patch that here as well.
Resolves issue #1657 (closed).