Comment 7 for bug 387573

That sounds like a usability hack, Textureglitch. You can already
scroll in unfocused windows as long as the cursor is over them, so
that would still work. And if you'd like to be able to type in
unfocused windows, then use focus-follows-mouse which allows this
globally. But like I said, scrolling in an unfocused window doesn't
give it focus so you could still do what you are talking about
regardless. The current behavior is inconsistent with other applets
and applications and I think is a confusing and annoying experience to
most users most of the time.