Feature request: detect browser prefetch

[feliperaul]

It would be nice to have browser.prefetch? that detects if the request is coming from a Omnibar prefetch that modern browsers perform.

This stackoverflow answer (https://stackoverflow.com/questions/9852257/http-header-to-detect-a-preload-request-by-google-chrome) tells that each browser vendor sends different headers, being:

• Chrome: Purpose: prefetch
• Firefox: X-moz: prefetch
• Safari: X-Purpose: preview

[StanBright]

That'd be very helpful.

[fidalgo]

As I've dig into this subject I will let here some useful documentation I've found about the issue, in case it can help anyone else:

• https://stackoverflow.com/a/2030947 (Safari and Facebook Preview)
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Link_prefetching_FAQ#as_a_server_admin.2c_can_i_distinguish_prefetch_requests_from_normal_requests.3f