I think that was meant to delegate to some method for you to retrieve the current cart, nothing in relation to the 1.5.x BLC version. You could just use CartState.getCart().
Basically though, you should be doing all of the things that are in the BroadleafPaypalController.paypalProcess method in your own controller (if you don't want to just delegate to the BroadleafPaypalController).
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