Get List of Textures (or their names) used on Terrain?

I have a very similar question to the one that was asked over here: http://answers.unity3d.com/questions/220536/get-slope-and-colortexture-at-point-on-terrain.html

My issue with the answer that was provided is it makes the assumption that my "Rock" layer will be in a fixed layer of the alphamap. T$$anonymous$$s isn't my case. I may have levels with 0, 1, or many "Rock" layers. I don't want to have to constantly keep track of w$$anonymous$$ch textures are being used on each level. I'd like to write a simple editor script that keeps track of t$$anonymous$$s for me.

Every time I save the file, I want my script to just get each of my terrains, check the textures used, and store in an array w$$anonymous$$ch alphamap layers are "Rock" or not based on the name of the texture.

So my question is - how do I programmatically get the names of the textures used on a given piece of terrain? T$$anonymous$$s is happening in an Editor Script, if that helps. I figure it must be possible, because the Unity Editor keeps track of t$$anonymous$$s (or am I mistaken in t$$anonymous$$nking that all the pieces of the Unity Editor were built using these same classes that we have access to?)