This film is EMI/RFI protection. In this case it's preventing the RAM's noise from flooding the airspace with emissions which could interfere with either Bluetooth or WiFi radio signals.
Not sure why they used this method as most companies use a sprayed on ferris paint onto the plastic. The Iron particles held within the paint block some of the EMI but won't stop the RFI effectively. Here a copper foil would do better when it was also bonded to the metal chassis.