More types should be Serializable

[sandersdan]

In addition to VideoFrame and AudioData, other interface types should be serializable:

• EncodedAudioChunk
• EncodedVideoChunk
• VideoColorSpace (not yet in the spec)

It may make sense to add close() and add transfer to EncodedAudioChunk and EncodedVideoChunk, but they are immutable by design and therefore do not need transfer to avoid copying.

[padenot]

This will be quite useful, yes.