Notably:

• 3p.ampproject.net
• d-*.ampproject.net
• cdn.ampproject.org
• amp-error-reporting.appspot.com

This is following discussion from an email thread with @cramforce @erwinmombay @dknecht.

I suppose we could simply replace all of the URL strings sprinkled throughout the codebase with references to corresponding keys in window.AMP_CONFIG. I'm somewhat new to the codebase, but if that's the way forward, then I'd be happy to contribute.