- don't mutate PATH_INFO in env, test
- test fallback content type matches Rack::File
- change assertion style
- make HTTP_ACCEPT_ENCODING comparison case insensitive
- return gzip path from method instead of true/false so we don't have to assume later
- don't allocate un-needed hash.
Original comments:
https://github.com/rails/rails/commit/
cfaaacd9763642e91761de54c90669a88d772e5a#commitcomment-7468728
cc @jeremy
