Tweak or program that leaves an invisible function box on foreground?

I think I figured out a rather odd bug or glitch. Whenever I watch Youtube videos on full screen or play League of Legends on OS X, it lags. The frame rate drops heavily (on YT, it's clearly choppy, on League I play at 30 FPS).

But whenever I'm changing the volume or changing screen brightness, or any of the F1-F12 buttons that brings up the foreground box indicating some change, the videos stops being choppy and League jumps to 60 FPS.

So it made me wonder if there's some tweak out there that leaves an invisible box like that constantly hovering, but not actually changing anything like volume or brightness. It's just invisibly there, serving no purpose other than raising FPS (which I don't know why it does that).

 

I'm actually on a cMBP 15", 2012 mid