class EnableSameOutputBufferConcurrentlyInFlight

This informs the StreamProcessor that the client is prepared to handle

output packets that specify the same buffer as another packet that's

also concurrently in flight to the client (not yet recycled).

Most bitstream formats don't do this. In formats that can do this such

as VP9, most actual bitstreams don't do this.

As an example, in VP9, a stream can cause the same output buffer to be

used by another emitted output packet/frame by using show_existing_frame

on the same VP9 reference/held frame slot more than once without

decoding a new frame into that slot in between.

Clients that need to achieve full bitstream spec compliance for such a

bitstream format must send this message.

If this message is not in effect, the server will omit any such output,

which can result in output that is not compliant to the relevant

bitstream spec, and which can be visually different than the stream

intended.

Sending this message more than once closes the channel. If sent, this

message must be sent prior to the client establishing the first output

buffer_lifetime_ordinal.

This message is only permitted when

`[fuchsia.mediacodec/CodecFactory.DetailedCodecDescription.supports_dynamic_buffers]`

is true.