After a message is saved asynchronsly, fire an event and pass the
message attributes to frontend listeners via the chrome-runtime API.
This behavior is similar to the 'storage' event fired by localStorage.
Runtime reload is overkill and causes a jarring ux. Instead, send and
receive messages across the runtime. Also, if we need to jump between
the main ui and options pages, simply navigate within the current tab
rather than spawning a new one.
