[ttml2] Pull Request: Clarify constance of ECP and EPP (#860).

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

== Clarify constance of ECP and EPP (#860). ==
Closes #860.

See https://github.com/w3c/ttml2/pull/867

Received on Thursday, 28 June 2018 23:34:26 UTC