Summary:
Before we dropped all messages if the client connected before the device has been registered. Which happens typically on iOS (it can actually take very long, will investigate that as well, but not in this diff).
However, we don't need to wait for the device to process messages, we just need its serial, which we already know (given that we use that query id to find the matching device in the first place).
I think this will greatly improved perceived stability for iOS
Reviewed By: jknoxville
Differential Revision: D20734892
fbshipit-source-id: f98e8d31558ef606b9a8287e03fc41ab6c3a087d
f803cb3cb1