Semantically and practically, there's not much difference between "DEBUG" and "INFO" MEDIA_LOG levels currently. However, having a distinct "WARNING" level can help short-cut root-causing ERRORs (such as deprecation or detected-known-issue logs).

This bug tracks:
1) Changing most of the existing DEBUG to INFO, leaving only warnings and change DEBUG to be WARNING.
2) Document each of ERROR, WARNING, and INFO MediaLog levels in the code.

(At minimum, note that ERROR log entries' content can be exposed to the web app via MediaError.message, so must not expose pointer addresses, for example.)