Bug 1112135 - [Messages] When starting as an activity/notification/, delay threads rendering until the right panel is open. r=julien

Yeah I have mixed feelings about that, having dependency on the launch path - bad, but I still feel better if we talk to wrapper around non-standard ```mozMobileMessage```. Probably it's because of my previous draft work for DataStore, where I moved all mozMobileMessage dependencies to MessageManager and inside was able to switch between ```mozMobileMessage``` and DataStore to make it transparent for the consumer code. + some intent to make SMS app work in other browsers (but yeah, it's not priority at all, if we need to sacrifice this for the sake pf performance) :) So if you don't mind I'll keep it that way at least for now :)