Replace RTCEncodedVideoFrameType by WebCodecs EncodedVideoChunkType

[youennf]

---

Preview | Diff

[alvestrand]

This change removes the "empty" value. Are we clear that we don't need this one?

[youennf]

Fixes #278.

[youennf]

Are we clear that we don't need this one?

The only case where empty may be used in Chromium is after the video frame is written/transferred.
But this is not specced anywhere and it does not seem that useful.

@guidou, thoughts? Would you like any clarification work as discussed in #278?

[guidou]

Chromium uses "empty" only with the old API. With the standard version the frame keeps old metadata values after writing (at least the tests test that and implementations do that), so "empty" is never used in the spec and can be removed.