[mumphster]

If you just want porn you can cast an entire tab to your ChromeCast and just fullscreen the video. Works fine with sites like Twitch.TV too.

[w1ntermute]

Tabcasting currently only works with PCs, and not with Android. Android support is coming soon though.

[Crito]

Tabcasting also has godawful performance for me on Linux (running on a chromebook pixel no less). I assume the problem is they are doing software encoding of your tab instead of hardware, but I haven't investigated this.