10.12 Content-Length

								A
      valid Content-Length field value is required on all HTTP/1.1 request
      messages containing an entity body.

Not so if the entity body uses Transfer-Encoding: chunked.

Perhaps we should say:
HTTP/1.1 request messages that contain an entity body MUST contain
either a valid Content-Length field value or a Transfer-Encoding: chunked
entity header and a chunked entity body.

Dave Kristol