Everybody is so quick to forget about "Android fragmentation," but fragmentation is a clear indicator of Google's lack of control over Android.
In reality almost everyone nicely complies with google's compatibility definition, constraining how far they can fork android, just in order to get access to google's closed source apps: https://play.google.com/store/apps/developer?id=Google%20Inc...
Only amazon has managed to make a viable usable fork of android that complies with legal requirements, and the amount of work it took them was prohibitive for anyone not on amazon's scale.
Android as OS is open source, but android as experience is very much under google's control. Like i said though, they have been quite benevolent, because they view android as a vehicle to get you to use the google services.
Not to hundreds of millions of Chinese Android users.
The point of the CCD [1] is to ensure that new devices can run a test suite that ensures they work correctly with Android as it currently exists. CCD isn't just about Google Play and Google Play Services, its about the fundamental functioning of the OS.
[1]: http://static.googleusercontent.com/external_content/untrust...