Youtube plays sound while turning off the screen (IOS)
1. open youtube.com with Safari browser.
1.1 change to desktop mode
2. play content that you need to listen to.
3. scroll down the screen that will show the media control.
4. pause and turn off the screen.
5. turn on the screen, play it, and listen to the sound.
6. turn off again and do anything
note: while the screen is off,it can play only 1 content (not continue)
