Replace a few plumb-throuh functions on Font.

Instead, they should be accessing FontDescription and
querying it directly. This another step toward
weaning Blink off Font as a font-god object.

BUG=319475
R=ksakamoto@chromium.org,eae

Review URL: https://codereview.chromium.org/148063004

git-svn-id: svn://svn.chromium.org/blink/trunk@165895 bbb929c8-8fbe-4397-9dbb-9b2b20218538