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Wanted to update this as I took the flight myself in November.
There is absolutely no problem with carrying an electronic on your hand luggage. Dubai does have a secondary security check for flights departing to the US right before the boarding gates, but the security personnel will not ask you to turn your device on. Therefore, the functioning state of the device will not matter.
Upvote:2
Note that
By coincidence, very recently I flew Dubai->US (I can't remember if it was IAD) and I had a huge ... HUGE ... pile of Nintendo Switch and similar devices in my carry on. No issue. Nobody even noticed. By all means, things can change on a dime but honestly I feel there is not the slightest chance you will have a problem. (Oct 2018.)
If you want, you can just throw such junk in your checked baggage, it makes life much easier. There is no reason to take it in carry-on.
(Note: in the past, most people would say "Don't check laptops! They could be stolen! Damaged!" Nowadays, it's not such an issue. Sure, if you have a $zillion gaming laptop, take it onboard!)
No problems, enjoy!