[EME] Users of "persistent-release-message" (secure proof of key release for non-persistent licenses)?

Several of the open bugs that have been proposed for discussion at the f2f
relate to "persistent-release-message
<https://w3c.github.io/encrypted-media/#idl-def-MediaKeySessionType.persistent-release-message>"
sessions. Other than Mark, is anyone planning to use such sessions in an
application? If so, please reply with information about your use case
before the telecon on March 31, to give the group time to plan for possible
face-to-face discussion.

Note: This session type specifically relates to persisting a secure proof
of key/license release for *non-persistent* licenses for later retrieval.
It does *not* apply to release messages related to persistent licenses (“
persistent-license
<https://w3c.github.io/encrypted-media/#idl-def-MediaKeySessionType.persistent-license>”
sessions) or even release messages from “temporary” sessions that do not
need to be persisted.

David