[whatwg/fetch] Private (conceptual) trailer support (#980)

To support something like https://w3c.github.io/server-timing/#server-timing-header-parsing-algorithm the response concept needs trailer support. I'm not sure if we need to add conceptual request trailer support as part of solving this issue as I'm not sure there are any dependencies. But any design should work for them as well, I suppose.

Per HTTP semantics trailers (a header list) can arrive "concurrently" with a message body and they can arrive multiple times (i.e., an asynchronous sequence of header lists). Server Timing does not appear to account for that.

(See #772 and #979 for prior takes on response trailer support.)

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/whatwg/fetch/issues/980