It's always been the case that in production, Tornado dumps all the
event queues when shut down so that they can be reloaded by the
replacement Tornado process. This never worked in development because
the codepath for auto-reload didn't go through either a signal or
sys.exit (it re-execs the process instead).
This meant that we didn't have a mechanism for testing the event queue
dump/load functionality in the development environment. We fix this
by adding such dumping/loading. However, this breaks the automatic
reloading of open browser windows on a server restart, so we add that
back in by adjusting the special `restart` events to pass a special
`immediate` flag when used in development.
This also has the benefit of removing the "Bad event queue" errors one
would get on every file save induced restart on the Python console.
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