Get request Header count efficiently

[ddevienne]

There's no accessor for how many headers are on the request.

And HttpRequest::HeaderIterator is only a forward iterator,
thus std::distance() must walk the headers which is O(N) instead of O(1).

Sure N < 50, still, the HttpParser knows how many headers it parsed,
so couldn't it tell the HttpRequest, and we'd have an accessor?

[uNetworkingAB]

I ran a benchmark with and without iterating over the headers. It's not measurable, doesn't move the needle.

So while technically true, it's not a problem

[ddevienne]

Thanks for taking the time to benchmark it.

I still think it wouldn't hurt to record in the request what the parser already knows.
But not doing anything is obviously cheaper :).