Unconditionally return the height for the minimum width when doing get_desired_height()

Unconditionally return the height for the minimum width when doing get_desired_height()

This is the correct support for the opposing orientation for widgets
that support height-for-width, in an interface that was realized as
width-for-height, a height-for-width supporting widget should return
the minimum height for the minimum width when the initial
get_desired_height() is run.