Code review comment for lp:~josharenson/unity-system-compositor/handle_screenshot_button

unfortunately, this in combination with
https://code.launchpad.net/~josharenson/unity8/physical_keys_filter/+merge/244244
didn't test out too well.
see (videos: most comon restul https://www.youtube.com/watch?v=WpFQHptyGe4 , then i got a couple of weird ones where the lock screen didn't engage right https://www.youtube.com/watch?v=CjkZXn-Io_8 )