Dunno, but older airplane lavs have a used razor blade slot, so it's not like shaving in the lav is considered taboo. Come to think of it, I think I've also seen 110v outlets in lavs for electric razor users. I wouldn't worry about it. As long as you didn't hog the lav for an inordinate amount of time, lettem wait.

Seems when I'm waiting to use the lav, someone ahead of me takes 10 minutes or more. When I'm in the lav, I hurry so nobody in line is thinking "Why is that jerk taking 10+ minutes and what could they possibly be doing that takes so long?"

The flip side is that you could have shaven in the restroom immediately after customs/immigration. Arrivals Lounges are wonderful for cleaning up.