Add SkTypeface::getVariationDesignPosition.

Allow users to query a typeface's position in variation design space.

Change-Id: I173ee9eefdddee6b2613435ebcc6b08c25b382ed
Reviewed-on: https://skia-review.googlesource.com/8684
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Mike Reed <reed@google.com>
29 files changed