Move TypesettingFeatures from Font to FontDescription.

It's a value that was computed from FontDescription and cached
on Font. Why not just keep it on font?

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

Review URL: https://codereview.chromium.org/131453011

git-svn-id: svn://svn.chromium.org/blink/trunk@166640 bbb929c8-8fbe-4397-9dbb-9b2b20218538