[fxtf-drafts] Pull Request: [motion] Supply size in ray examples

ewilligers has just submitted a new pull request for https://github.com/w3c/fxtf-drafts:

== [motion] Supply size in ray examples ==
size is now required. The examples now show size explicitly.

The polar placement examples assume the rays begin at the center
of the body. We now make that explicit by setting left/top or by
setting offset-position.

See https://github.com/w3c/fxtf-drafts/pull/164