[whatwg] First or last Content-Type header?

[Adam Barth]

In editing the content sniffing Internet Draft today, I noticed the
draft uses the *first* Content-Type header.  Internet Explorer uses
the first Content-Type header, but Firefox and Google Chrome use the
last Content-Type header.  (I don't recall off-hand which Safari or
Opera use.)  Because the sniffing algorithm is more similar to the
algorithms used by Firefox and Google Chrome, I've changed this aspect
to match them as well.

Adam