Enable universal accelerated overflow scroll

LayoutTests/virtual/softwarecompositing/overflow/automatically-opt-into-composited-scrolling-part-3-expected.txt

-Testing permutation set 2 - this means that the "sibling" will be placed at the index 2 of the paint order.
-PASS iteration 0: did not opt in, since doing so would change the stacking order.
-PASS iteration 1: did not opt in, since doing so would change the stacking order.
-PASS iteration 2: did not opt in, since doing so would change the stacking order.
-PASS iteration 3: did not opt in, since doing so would change the stacking order.
-PASS iteration 4: opted in, since doing so does not change the stacking order.
-PASS iteration 5: opted in, since doing so does not change the stacking order.
-PASS iteration 6: did not opt in, since doing so would change the stacking order.
-PASS iteration 7: did not opt in, since doing so would change the stacking order.
-PASS iteration 8: opted in, since doing so does not change the stacking order.
-PASS iteration 9: did not opt in, since doing so would change the stacking order.
-PASS iteration 10: did not opt in, since doing so would change the stacking order.
-PASS iteration 11: did not opt in, since doing so would change the stacking order.
-PASS iteration 12: did not opt in, since doing so would change the stacking order.
-PASS iteration 13: opted in, since doing so does not change the stacking order.
-PASS iteration 14: opted in, since doing so does not change the stacking order.
-PASS iteration 15: did not opt in, since doing so would change the stacking order.
-PASS iteration 16: did not opt in, since doing so would change the stacking order.
-PASS iteration 17: opted in, since doing so does not change the stacking order.
-PASS iteration 18: did not opt in, since doing so would change the stacking order.
-PASS iteration 19: did not opt in, since doing so would change the stacking order.
-PASS iteration 20: did not opt in, since doing so would change the stacking order.
-PASS iteration 21: did not opt in, since doing so would change the stacking order.
-PASS iteration 22: opted in, since doing so does not change the stacking order.
-PASS iteration 23: opted in, since doing so does not change the stacking order.
-PASS iteration 24: did not opt in, since doing so would change the stacking order.
-PASS iteration 25: did not opt in, since doing so would change the stacking order.
-PASS iteration 26: opted in, since doing so does not change the stacking order.
-