Enable universal accelerated overflow scroll

LayoutTests/compositing/overflow/resources/build-paint-order-lists.js

-function getPaintOrder(element)
-{
-  var divElementsBeforePromote = [];
-  var divElementsAfterPromote = [];
-
-  var paintOrderListBeforePromote = window.internals.paintOrderListBeforePromote(element);
-  var paintOrderListAfterPromote = window.internals.paintOrderListAfterPromote(element);
-
-  for (var i = 0; i < paintOrderListBeforePromote.length; ++i)
-    if (paintOrderListBeforePromote[i].nodeName === "DIV")
-      divElementsBeforePromote.push(paintOrderListBeforePromote[i]);
-
-  for (var i = 0; i < paintOrderListAfterPromote.length; ++i)
-    if (paintOrderListAfterPromote[i].nodeName === "DIV")
-      divElementsAfterPromote.push(paintOrderListAfterPromote[i]);
-
-  return {"beforePromote": divElementsBeforePromote,
-          "afterPromote": divElementsAfterPromote};
-}
-
-function comparePaintOrderLists(oldPaintOrder, newPaintOrder)
-{
-  if (oldPaintOrder.length !== newPaintOrder.length)
-    return false;
-
-  for (var i = 0; i < oldPaintOrder.length; i++)
-    if (oldPaintOrder[i] !== newPaintOrder[i])
-      return false;
-
-  return true;
-}
-
-function countOccurrencesOfElementInPaintOrderList(paintOrder, element) {
-  var occurrenceCount = 0;
-  for (var i = 0; i < paintOrder.length; i++)
-    if (paintOrder[i] === element)
-      occurrenceCount++;
-
-  return occurrenceCount;
-}
-
-function compareStackingOrderWithPaintOrder(stackingOrder, paintOrder)
-{
-  if (debugMode) {
-    write("paint order:")
-    for (var i = 0; i < paintOrder.length; i++)
-      write(paintOrder[i].id + " " + paintOrder[i].className + " " + paintOrder[paintOrder.length - i - 1].tagName);
-
-    write("stacking order:")
-    for (var i = 0; i < stackingOrder.length; i++)
-      write(stackingOrder[i].id + " " + stackingOrder[i].className + " " + stackingOrder[i].tagName);
-  }
-
-  if (stackingOrder.length < paintOrder.length)
-    return false;
-
-  // We expect the stacking order list to contain more than the paint order
-  // list sometimes because after we promote, the container's children won't
-  // appear in the stacking context's ancestor's lists anymore (which is
-  // expected and correct).  They'll still be in the stacking order list.
-  // The important part is that the order of the things present in the paint
-  // order list is preserved in the stacking order list.
-  for (var i = 0, j = 0; i < stackingOrder.length && j < paintOrder.length; i++)
-    if (stackingOrder[i] === paintOrder[paintOrder.length - j - 1])
-      j++;
-
-  if (debugMode)
-    write(stackingOrder.length + " " + i + " " + paintOrder.length + " " + j);
-
-  return j == paintOrder.length;
-}
-
-function testPaintOrderListPermutation(count) {
-  if (!window.internals)
-    return;
-
-  var container = document.getElementById('container');
-
-  window.internals.setNeedsCompositedScrolling(container,
-      window.internals.COMPOSITED_SCROLLING_ALWAYS_OFF);
-
-  var oldStackingOrder = getStackingOrder(container);
-  var oldPaintOrder = getPaintOrder(container);
-
-  window.internals.setNeedsCompositedScrolling(container,
-      window.internals.COMPOSITED_SCROLLING_ALWAYS_ON);
-
-  var newStackingOrder = getStackingOrder(container);
-  var newPaintOrder = getPaintOrder(container);
-
-  window.internals.setNeedsCompositedScrolling(container,
-      window.internals.DO_NOT_FORCE_COMPOSITED_SCROLLING);
-  // The getPaintOrder() function should return a pair of paint orders.
-  // One before promotion and one after. This pair of lists should remain
-  // identical whether the element is actually currently promoted or not,
-  // its purpose is to generate hypothetical pre- and post-lists to
-  // determine if the element is promotable.
-  if (!comparePaintOrderLists(oldPaintOrder, newPaintOrder))
-    write("iteration " + count + " FAIL - paint order lists not identical before/after promotion");
-
-  if (!compareStackingOrderWithPaintOrder(oldStackingOrder, oldPaintOrder.beforePromote))
-    write("iteration " + count + " FAIL - paint order list before promote doesn't match stacking order");
-
-  if (!compareStackingOrderWithPaintOrder(newStackingOrder, oldPaintOrder.afterPromote))
-    write("iteration " + count + " FAIL - paint order list after promote doesn't match stacking order");
-
-  var containerOccurrences = countOccurrencesOfElementInPaintOrderList(oldPaintOrder.beforePromote, container);
-  if (containerOccurrences !== 1)
-    write("iteration " + count + " FAIL - paint order list before promote contains " + containerOccurrences + " occurrences of container. Should be exactly 1.");
-
-  containerOccurrences = countOccurrencesOfElementInPaintOrderList(oldPaintOrder.afterPromote, container);
-  if (containerOccurrences !== 1)
-    write("iteration " + count + " FAIL - paint order list after promote contains " + containerOccurrences + " occurrences of container. Should be exactly 1.");
-}
-
-function runPaintOrderPermutationSet(permutationSet) {
-  runPermutationSet(testPaintOrderListPermutation, permutationSet);
-}