There's this Chrome Extension I dug up, because I really like just hitting the Left or Right arrows on my keyboard to fast forward or rewind. (Let's be honest—I use it to rewind because I wasn't paying attention to the movie.)
Long story short, I reviewed the code and found a block that was commented out, which would allow for fullscreen mode. So I did what any sane web developer would do and I added it back in, utilizing a different method to the original developer's which actually worked.
And then I went and refactored the whole gosh darn thing! I don't know what even possessed me to do that, but here we are.