I'm actually a software guy that a few years back saw that programming is going to be too cookie cutter and the real need will be in hardware/robotics.
But as I mentioned, the plugin/app can have the code ready and could scan your network for the Pi or like I did for the Windows Phone App, it has an input for an IP & you select what feature you want and hit "CAST".
However, most people will want the capabilities built-in to his/her browser. The problem with trying to use Googles built-in feature, we have no clue on how it truly works, what data it sends, how is it received, etc.
Also, how to get the Pi to even be recognized as a fake Chromecast as Google could be looking for SNMP, MAC Address (could be a set they own/use), and other possible items.
So, until Google opens it up (clearly seems not happening anytime soon) and even allows everyday people to make Apps (they're able to pick/approve), it won't be happening.
Which is why I made PiCAST to begin with. I didn't like how they closed everything down. It is evil, they're proprietary methods will make me continue to build something completely against them for as long as I have to.
I don't need the project, I have a Chromecast that I almost never use but its the open part that pisses me off when they act so high and mighty. They're collecting your use of the Chromecast, its all about info sharing, hence it being $35.