Fix my stupid sloppiness that led to a Prototype scrolling bug.

@kenearley @stof 

This reverts 6dc024dc5db3f449da30a1b13dade665e33278dc. Somehow I stupidly assumed that Prototype and jQuery could do anything the same way and apparently did not test this properly in any way.

I don't have an open bug, but a commenter in 64bbd1900dcc2f7154845122b38a9c42142ada3f has called it out.