We should investigate the benefit of using an n-squared algorithm to
traverse the rectangle List in RepaintArea.java. The idea would be to
go through the list removing and painting any rectangles that do not
intersect the rest of the list.

This is obviously more rectangle math, but we think that the penalty of
doing the extra rectangle math (done with integers) math is not as large as the penalty of possibly repainting an unnecessarily large area.

This is additional work for 4227116 to be done post-Kestrel.