The current specification now states that if the resource is redirected to a different origin, then this is treated as a failure and the local cached copy (or fallback) is used instead.
In section 5.6.4 of http://www.w3.org/TR/2011/WD-html5-20110525/offline.html it states that:
Redirects are fatal because they are either indicative of a network problem (e.g. a captive portal); or would allow resources to be added to the cache under URLs that differ from any URL that the networking model will allow access to, leaving orphan entries; or would allow resources to be stored under URLs different than their true URLs. All of these situations are bad.
So sadly you can't serve some pages from Amazon S3 or Cloudfront.