This is the actual fix for the bug. This changes the vertical sizing of
inline ::first-letter frames to work like inlines (and size based on
font metrics), so that the line-height calculation that happens later
will produces the same results as inlines would produce.
In the case we're concerned with of having a text frame child that's
0x0, this changes the inline ::first-letter from from being 0x0 to
having a height that is determined from the font metrics.
L. David Baron
Robert O'Callahan