@jensimmons Because feedback was requested:

I will not use this until a better contrast calculation algorithm has been implemented. APCA has been shown to be superior in every real-world test I have seen. While I'm happy that you've indicated willingness to replace it later, I would have loved to see more leadership from the Webkit team. Please adopt a superior contrast scoring method (APCA) instead of a demonstrably broken algorithm that is divorced from how we perceive colour and contrast.