(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
By default, a Window has a minimum size of 50x50 - ComboBox lists aren't
always this tall. We now set the minimum height of the ComboBox Window
according to the height of three items, or the total height of all the
items in the list, whichever is smaller.
This means there is no longer any unpainted space in the list window
due to the shortfall between the ListBox widget and Window heights,
and the ComboBox list window always remains a comfortable height for
viewing. :^)