This is extra important in the tests where we expect no changes to the
display, as otherwise we can't tell the difference between success and a
decoder that is simply waiting for more data.
These are very pointless for the server to send, but not a violation of
the protocol so we need to be able to handle them. We've seen this
happen in real world scenarios a few times.
This is what the browser wants so it avoids having to spend time
converting everything. Unfortunately it usually means the server instead
needs to convert it for us, but we assume it has more power than we do.
Pierre Ossman