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A lot of their products are built with GWT https://developers.google.com/web-toolkit/

which compiles the client side code automatically.

So its more that the code is auto-generated (and because its generated it doesnt need to be readable), rather than deliberately obscured.

Google has turned GWT over to an external team and is no longer using it for new apps.

Google has been using AngularJS for some new sites.

But no matter how you do it, single page apps usually result in a heavily minified representation.