Z order in based on the position in the Hierarchy is reversed in 4.9

The Z order that is given to a widget based on it's position in the Hierarchy panel in 4.9 goes from bottom of the hierarchy to the top (The bottom widget is the front most widget) instead of the top to bottom (The top widget is the front most widget). In 4.8 the Z order was given based on Top to bottom. This means that any developers upgrading to the 4.9 version will experience issues.

1. Open the Editor
2. Create a new widget blueprint
3. Add three images of different colors to the designer tab (attached image for reference)
4. Notice that the image at the bottom of the hierarchy is always in front

Expected: The Z order given due to hierarchy would be consistent between versions
Result: The Z order given due to hierarchy has been reversed between versions