Add new motion for when Folder preview changes due to onDrop.

Instead of changing the display order of the Folder to preserve
the upper left quadrant, we are opting to change the Folder Icon
preview to always show the upper left quadrant.

This means that when adding items to a Folder, the preview items
may change. (They will change when the column size increases).

Bug: 27944225
Bug: 63140071
Change-Id: I863c2479469d68559cab2878030c2087d48217d6