I've disabled go full screen
I hate you.
But seriously, why? Just whyyyy? :'-( There are very, very, very few games that benefit from this. Your's aint such a game. It is non fun to scroll down and up or resize browser window to actually see your game in full. I cannot turn my display in portrait mode. (Ok, sure, I could, with the graphics diver and turn my neck 90 degree, since I am talking about a computer screen)
Since basically all the unity games out there do handle this in the expeced manner, I guess you and op are missing something trivial and overdo something that should be handled by Unity automatically.