OK so I have worked in Sweden for 20 years, and deiced thousands of aircraft.
I have never seen the abbreviation CSFF before, or heard the expression. So I suppose it is a Boeing NG phrase, as I have managed to miss that aircraft so far.
But looking at the original photo, I can't see that being frost. It looks like deicing fluid that has frozen on the wing, perhaps being applied long before departure as RYR 738 said.