[1]https://support.google.com/adsense/answer/16737?hl=en
[2]https://developer.chrome.com/webstore/program_policies (ctrl-f, then search for "Interfering with Third-party Ads and Websites")
Edit: Hmm, below is correct. The "single purpose" policy is pretty hard to understand, and the reason Google gave for banning it. The policy above would seem more applicable.
The description of that rule also doesn't seem to apply: "Ads associated with your app must not interfere with other apps, ads, or the operation of the device, including system or device buttons and ports." It's specifically under the ads section of the policy.
I'm not sure the policy applies in any way to Chrome either: "...ensure that together we continue to deliver the world's most innovative and trusted apps to over a billion people through Google Play." EDIT: The link has been changed and now points to the equivalent Chrome Store policy. My other 2 points remain true though.