Introducing Backpressure mechanism for live collaboration

[vjeux]

On underpowered device, it's easy to come into a situation where updates are backing up and it's rendering updates from a few seconds ago makes for a really bad experience. Instead what we should do is to start dropping updates if we are getting backed up so that we render frames not too far away from the current one to avoid introducing massive lag.

[vjeux]

cc @petehunt as it's in your alley.

[tomayac]

WebSocketStream might come in handy here, since it comes with back pressure support.

[blairmacintyre]

I'm seeing massive lag on even high-end devices during collaboration right now. Desktop mac, PC, iPhone, and iPad.