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.
At first I was thinking about removing threadless drafts on ```drafts-changed``` and re-rendering them again, but what if user already opened that draft from main app instance. Anyway, I'd rather move this use case to a separate bug, what do you think?