Back button doesn't exit video player when using TV UI on phone/tablet
Description
When TV UI is selected on a tablet/phone, back button doesn't exit video player, it just hides the UI.
Expected behavior
Back button should exit video player on a tablet/phone.
Actual behavior
Back button only hides the UI, just like on android TV.
Steps to reproduce
- on a phone or tablet, select TV UI in settings
- play any video
- touch the screen to show overlay, and press back button
App version
latest git (3.4.0 Beta 4)
Freebox Pop (android TV 9) Nvidia shield Tablet K1 (android 7) Sony Xperia XZ2 (android 10)