Sprite Editor Unity 4.6: green box and Border parameters, what are they for?

It seems, that those green boxes in the 2d sprite editor are new in Unity 4.6.
Also the Border parameter.

In the Manual they aren’t mentioned…
Unity Manual Sprite Editor

So, what are they for?

Don’t have Unity in front of me right now, but I’d guess the borders are used for creating 9-slice sprites. Further, I’d guess that the green box is just a visualization of the defined borders.