On slow networks sometimes escape sequences were being partially
consumed, causing junk to be added to the editor when you pressed arrow
keys and so on. Now we have a way to wait.
Empirically seems to work if I page-up and then scroll back up using
up-arrow. Before I'd consistently get junk even on my local machine. Now
I no longer do.
If we still see problems I'll increase the wait time and see if the
increase helps. Then we'll know more about this approach.
