As noted in the comment of Morph>>addMorph:fullFrame:, there is an
inconsistency between the meaning of layout offsets between ordinary
Morphs and SystemWindows.  This is emphasized by the fact that
SystemWindow>>addMorph:fullFrame: actually negates the bottomOffset
(in addition to adjusting it to take the title bar into account) --
but only when the bottomFraction is not 1.0!

This should really be cleaned up.  I'd set to it straight away, but to
make matters worse, it looks like LayoutFrame in fact wants to treat
the offsets as insets, causing me significant cognitive dissonance.
So: should "offsets" be offsets, should "offsets" be insets, or should
the name be changed so that "insets" are insets?

-Jesse