rails/rails — pull request #15012 by schneems (2014-05-07 17:02:10+00:00)
Title: HTTP::Headers#key? correctly converts

Previously if you were looking for a given key, the header may incorrectly tell you that it did not exist even though it would return a valid value:

```ruby
env = { "CONTENT_TYPE" => "text/plain" }
headers = ActionDispatch::Http::Headers.new(env)
headers["Content-Type"]
# => "text/plain"

headers.key?("Content-Type")
# => false
```

This PR fixes that behavior by converting the key before checking for presence