Remove unused font-smoothing code from Font.

The value is queried in FontMac, but it never changes.

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

Review URL: https://codereview.chromium.org/158173004

git-svn-id: svn://svn.chromium.org/blink/trunk@166772 bbb929c8-8fbe-4397-9dbb-9b2b20218538