This is a preparator refactor for supporting hosting different Tornado
processes on different servers; to look up which Tornado server we
should be sending the event to, we'll need the realm object.
For some reason in my original version I was sending both
content and data to the client for submessage events,
where data === JSON.parse(content). There's no reason
to not just let the client parse it, since the client
already does it for data that comes on the original
message, and since we might eventually have non-JSON
payloads.
The server still continues to validate that the payload
is JSON, and the client will blueslip if the server
regressses and sends bad JSON for some reason.
Tim Abbott
Steve Howell