From: https://chromium-review.googlesource.com/c/chromium/src/+/1383434/1/third_party/blink/renderer/modules/mediasource/media_source.cc#813

Dale's Q's:
Can an ObjectURL be used twice with MediaSource?
Can you revoke it automatically if it was used with this MediaSource object?

https://github.com/w3c/media-source/issues/156 has a lot of context on this. An objectUrl is not auto-revokable (though Firefox might be doing this). If they are, we may be able to experiment in Chrome with making them auto-revoked (though we would need to be careful to highlight that this makes the createObjectUrl(MediaSource) different from all other compliant createObjectUrl(..) for which the URL API produces non-auto-revoking objectUrls.

If the such an experiment succeeds, we could fix the problem mentioned in this code comment, making a MediaSource objectUrl useable at most once for attachment to HTMLME.