Document http "aborted" events

[kemitchell]

Checklist

• make -j4 test (UNIX) or vcbuild test nosign (Windows) passes (This PR just adds doc)
• a test and/or benchmark is included (This PR just adds doc)
• documentation is changed or added
• the commit message follows commit guidelines

Affected core subsystem(s)

doc (for HTTP)

Description of change

This pull request follows on #6925 (in which @Fishrock123 and @dougwilson made key appearances) to document the "aborted" (as opposed to "abort") events emitted on HTTP requests and responses on socket closure by the remote system.

A few links from the issue that seem most relevant:

• HTTP client emitting 'aborted' from the corresponding response (req.res).
• HTTP server emitting 'aborted' from requests.
• The test for 'aborted'

The last tests the event on req from the server point of view. I actually don't see a test checking the event from the client API. This test sets a handler on a res from an http.get call, but as far as I can tell there's no test verifying its functionality. I can try and cook one up if needed.

_Be Warned! This is my first PR to Node.js. I reread CONTRIBUTING, but probably screwed something up anyway. Many thanks to team for patience and understanding!_

This PR coming to you live from doc sprint at NodeConf Adventure.

[addaleax]

I think you can squash the commits together and add an Fixes: https://github.com/nodejs/node/issues/6925 line (of course, that can also be done upon landing).

This looks good to me, but my knowledge of the HTTP implementation in core is not too extensive, so /cc @nodejs/http

[jasnell]

LGTM, the commits can definitely be squashed but that can be done by whomever lands.

[kemitchell]

Separate PR for a test checking aborted events on client response objects? Or am I still missing something?

[addaleax]

Landed in 86fdbe0

Many thanks, and I think it’s safe to say that a separate PR for testing this event on client responses would be appreciated! :)