Wait. So all this commit does is remove support for these browser fixes unless compat is enabled? How does this work without the compat layer for those browsers? I.e. if you build this without compat, does this function no longer work? If `hasGetBoundingClientRect` is `false` and the user viewing a page on firefox, what's the result?

We should be replacing the code with feature detection entirely. If all the affected browsers have `hasGetBoundingClientRect` then you don't need to keep the browser sniff code in compat. Right?