FWIW, so far I've tested this change against:

cherrypy 3.6.0
uwsgi 2.0.9 (--http-raw-body)
nginx 1.6.2 (chunked_transfer_encoding on, proxy_buffering off;) + uwsgi 2.0.9 (--http-raw-body)

The chunked body works as expected. Unfortunately, all implementations seem to be ignorant of the trailer part. So it seems that although RFC-compliant (and I can definitely see the use case for it), they trailer implementation may not be overly practical. I still think that it's worthwhile keeping it, but perhaps adding a note that it may not be supported at this point.

Relevant gists: https://gist.github.com/demianbrecht/3fd60994eceeb3da8f13