You may have missed this but Google Cloud CDN can now sit in front of GCS: https://cloud.google.com/compute/docs/load-balancing/http/us...

Feel free to ping me with your project id if you need to be whitelisted for the Alpha.

Disclosure: I work on Cloud at Google, so I'm trying to win your business.

Does it support ssl for custom domains? AWS has a "certificate manager" service that integrates nicely(i.e provides free certificates, automatic renewall etc) with their CDN.