trying to understand Youtube Leanback implementation

in youtube leanback new application I can control the full-screen browser on my computer, using my android phone. I'm trying to understand - how does it work?

For example, when I press "play" the movie starts playing. Now when I press play, it probably sends "HTTP Post" to the youtube server; how does the youtube server push the request to "play" to the bro开发者_开发百科wser? with push notification? probably not, because it's not a reliable service maybe this application is written with the GAE Channel-API, and then there's a continuous communication between my browser and the server...

Any clue?

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I'm quite sure now they use the Channel-API. Might not be the same as is opened for the public with the Google App Engine platform, but since youtube has to do with Google, I think that is how it is done.