Medialog logs key IDs that are unavailable on playback
e.g.
https://cs.chromium.org/chromium/src/media/filters/decrypting_demuxer_stream.cc?rcl=62bc7e64cba8402799f24ade5b0bf5560a163a1b&l=292

It should also log the key IDs that are currently used. This should be done in the demuxer where it has constructs the decrypt configs.
Make sure it doesn't get too spammy.