Actually for Robin, there is a second condition: Do not sleep with her / reject her after playing video games at her house.This is just incorrect. There is only one condition that prevents Chris from having a chance with any of the three girls: If you get with the girl in-game. You can extrapolate the possibilities from there.
Allow me to ask again...How exactly do you get this ending? There is nothing about it in the written walkthrough and I think I've only ever seen Lexi's 'toilet' ending. There is only one dialogue choice (yes/no) in the golf club scene, but that doesn't appear to make a difference.