Constant ROUTE_HEADERS_WALK 

pub const ROUTE_HEADERS_WALK: &'static str;

The FOURTH walk: the headers of the response the matched route answered.

★ ONE WALK, TWO CONSUMERS, and that is the whole reason it exists rather than a routeHeader that reaches in on its own. __lgx_route_handler puts these on the response it hands the socket — which is how a Set-Cookie a route set actually reaches a browser — and routeHeader(method, url, name) reads one out by name so a test can see it without a server. Built arm-for-arm beside the other three, so it cannot disagree with them about which route matched.