Sent the first time a user is starting, to allow system apps to perform one time initialization. (This will not be seen by third party applications because a newly initialized user does not have any third party applications installed for it.) This is sent early in starting the user, around the time the home app is started, before Intent.ActionBootCompleted is sent. This is sent as a foreground broadcast, since it is part of a visible user interaction; be as quick as possible when handling it.