Matching hint responses with requests

[igrigorik]

Continuation of: igrigorik/resource-hints#5. For background see:

http://w3c.github.io/resource-hints/#matching-hint-responses-with-requests

[igrigorik]

Closing, this is a preload-specific bug for which we have note in the spec:
http://w3c.github.io/preload/#matching-responses-with-requests

[yoavweiss]

What happens when prefetching a non-cacheable resource? (I'm assuming that since prerender opens a hidden tab, non-cacheable resources would work just fine there)