The ScrollBar control reports boundsInParent / boundsInLocal bounds as being larger than they should be. If I comment out the inner shadow effect, then the bounds come out correctly. It appears that the call to effect.getBounds(xform, nodeInput) (line 33 of EffectFilter in scenario) is computing and returning the padded bounds as opposed to the content bounds which is what we would expect in this case.

The first attached picture shows the bounds when the effect is commented out, the second shows the bounds when the effect is in place.