While fixing RT-13275 I noticed some dirty region problems with some of its test cases. This could be a disagreement between the bounds calculated at the FX layer and the NG/Decora layer, but I didn't track it too far other than to note that the implementations between those two layers differ in their calculations of the fringe of affected pixels in blurs and shadows.

To reproduce:

1. Run the BlurTest.java example.
2. Check the "blue bg" checkbox for improved visibility.
3. Slide the blur sliders all the way to the right for maximum blur.
4. Play with the "mb angle" slider to adjust the angle of the Motion Blur.
5. As you slide the mb angle slider back and forth notice issues with the clearing/damage repair of its bounds.
6. Run the example with dirty opts off and notice that there are no rendering anomalies.

7. Do the same thing with the ShadowTest.java example.
8. (There is no "blue bg" checkbox, shadows are fairly visible by default.)
9. Max the blur sliders and play with the "ds spread" slider to see the damage repair issues.