This is a vanilla Rails 4.1 application, demonstrating that handling of chunked requests is incorrect.
> curl -X POST -H 'Content-Type: application/json' -H 'Transfer-encoding: chunked' -d '{"a":"b"}' http://localhost:3000/ && echo
{"controller":"application","action":"testing","application":{}}
# Uncomment git source for rails in Gemfile
# This is the expected output
> curl -X POST -H 'Content-Type: application/json' -H 'Transfer-encoding: chunked' -d '{"a":"b"}' http://localhost:3000/ && echo
{"a":"b","controller":"application","action":"testing","application":{"a":"b"}}