Diagnosis
That's hard water scale or detergent that hasn't rinsed off properly. The most common cause on this model is a clogged or malfunctioning rinse aid dispenser, or simply not using rinse aid.
How to Fix It
First, fill the rinse aid compartment (it's on the inside of the door). Set the dispenser dial to a higher setting (like 4 or 5) if your water is very hard. Then, run a cleaning cycle with a dishwasher cleaner like Affresh to clear out any scale in the lines and jets.
If That Didn't Work
The rinse aid dispenser solenoid might be faulty and not injecting rinse aid during the final rinse. Also, check that you're using a high-quality detergent formulated for hard water and not over-filling the detergent cup.
Heads Up
Using too much detergent in soft water can cause the same filmy residue. Match your detergent amount to your water hardness.