Shift-click for recipe?

[bsmorgan]

I've just been made aware that when the Blizzard tradeskill frame is open, shift-click on an item in your inventory craftable by that skill brings up the recipe for that item. Close the Blizzard tradeskill frame, and shift-click on the same item brings up the split stack frame.

Where do I find the code that implements this behavior? I'm not sure where to start looking.