Spark DataGrid Drag and Drop non functioning

Description

Dropping a dragged item onto the grid does not work. When calculating the DropLocation (in dragEnter, dragOver, dragDrop handlers) it falls through to LayoutBase.calculateDropIndex which simply executes "return target.numElements;" That's clearly not how the dropIndex should be calculated on the grid. The GridLayout class should be overriding this method and calculating it correctly.

Furthermore, upon trying to fix this issue (which is more complicated than it should be because DataGrid.calculateDropPosition() is marked as private) the DataGrid.calculateDropPosition() does not perform a null check on the DropLocation (which is valid value).

Steps to Reproduce
1. Create a DataGrid with dragEnabled, dragMoveEnabled, and dropEnabled all set to true.
2. Try dragging rows around and dropping them.

Environment
Windows 8, Apache Flex 4.14

Expected Behavior
Seeing the drop indicator.
The expected behavior of dragging a row and dropping it in another location.

Actual Behavior
No drop indicator. Dropping a row does nothing.