delay between expose events is high when rapidly scrolling a scrollpane

On a relatively slow machine (SS4) when scrolling the Hotjava User's guide
document (for example), the scrolling behavior when moving the thumb
rapidly in one direction or the other seemed to move in large steps.

My interpretation of the problem was that our paint process was too expensive,
so I timed it and found that the entire paint process was taking considerbly
less than 10 milliseconds, but we were only seeing paint events approximately
every 150 milliseconds. Note that 150 milliseconds is very approximate; it
ranged from as low as 40 to as high as 350.

On faster machines, this is not as apparent.