Does not work for iOS yet?
Edit: "At this time, WhatsApp Web is available only for Android, Windows Phone, Nokia S60, BlackBerry and BB10 smartphones." https://www.whatsapp.com/faq/en/web/28080003
Chromecast is pretty shitty. It often lags und quality is not great. The first time I saw it in action, it was pretty embarrassing for a Google manager who tried to demo something with it. I replaced mine with an Amazon Fire TV.
What's even more infuriating is that devices with LTE like razorg get delayed multiple weeks if not months with software updates. Still waiting on Android 5 with what I thought is the 'better' device compared to razor.