newStreams

The source's PlayerMediaSource.streams as they stand from this packet on, present only on the first packet a source hands out after its list changed, and null on every other packet (#509). It is the whole list: a stream is new when its index was not in the list before, and an entry that differs from the one before was corrected, as FFmpeg corrects a sound's sample rate at its first packet. Null for a source whose streams never change.