Control 'Picture in Picture' video with arrow keys

In Firefox , when you click on the Picture in Picture window, nothing visually shows that it's selected, but you can now use the arrow keys to control the video:
Left and Right arrows to go backwards and forwards in the video,
Up and Down arrows to change the audio volume.
When you click on a different website, the arrow keys no longer control the video (until you click it again).

This is far more efficient than needing to find the youtube tab just to go back 5 seconds to hear something you missed.

This would be great in Orion