Import maps a document's Arial to Liberation Sans (screenFontName) and the
model keeps it under that name, but only 'Arial' had an @font-face — so on a
machine without Liberation Sans installed every such run fell to the browser's
default serif. The bundled TTFs are now declared under their own family too,
as Liberation Serif already was.
Measured against LibreOffice on a 28-page fixture: its cover lines came out
7-16% narrow, 54 reports to 44.