Fix prefs migration for font settings.

BUG=112706
TEST=Verify font changes work when old preference values exist. See bug for details.
Review URL: https://chromiumcodereview.appspot.com/9749001

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@127707 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed