That Leviton wall outlet only puts out 3.4A total. (15A is the 120V rating). If you're going to run a wire from the wall outlet to a USB hub, IMO it's be better to run a power cord from the wall to a USB charger like the Anker charger I recommended. Still one wire from the wall to a small box and the short USB cables to each device being charged. There's more power available and you can take it with you.

I can see where that Leviton outlet would be useful on a kitchen counter top outlet where you might tend to charge your cellphone.