[ttml2] Pull Request: Add missing two component expression to <position> value syntax.

skynavga has just submitted a new pull request for 
https://github.com/w3c/ttml2:

== Add missing two component expression to <position> value syntax. ==
See issue #174.

See https://github.com/w3c/ttml2/pull/180

Received on Saturday, 10 September 2016 23:57:57 UTC