picture in picture should be 'always on top'

STEPS TO REPRODUCE

1. Visit YouTube. Watch video.
2. Double right click.
3. Choose picture in picture.
4. Open different window and make full screen.

OBSERVED RESULT Picture in picture is overlayed on top of all windows apart from full screen.

EXPECTED RESULT Picture in picture should also overlay full screen. If not, option 'always on top' should be above full screen if selected.

ADDITIONAL INFORMATION Using gnome at the moment which correctly handles pip mode. Even setting window as "always on top" in XFCE results in full screen still doesn't place it on top of full screen windows.

Example uses: Full screen game whilst watching a video picture in picture. Full screen browser whilst watching a video picture in picture.