Bug 1058459 - [SMS] Data shared from other applications are not shown as Drafts until the app is killed and open again.  r=schung

Using localStorage as inter app communication bus.
Maybe I'm wrong, but it seems we don't need this parameters currently. Would it be simpler to send the postMessage only with eventName as parameter? Because in other place you communicate the port only with simple string like 'closed'/'ping'/'pong', but emitted event from outside is exception. Using string or object both works for me(maybe object is more flexible in the future).  Just think that it would be safer if we got unified message parameter.