Automatically scrolls to the top of the video if it's in theater mode
Un-fixes the YouTube header and scrolls to the top of the video when you're watching in theater mode.
This saves you from having to manually scroll past the header when you're watching video in a small window and you go from a playlist to a video, or switch videos in a playlist.
Demo: https://www.youtube.com/watch?v=vpCoG5S1VAk
