rails/rails — pull request #3878 by kennyj (2011-12-06 17:02:16+00:00)
Title: Use default charset when we read content type without charset.

When we read Content-Type header without charset, we should use Response#default_charset .

The original code is 'UTF-8' (string literal).
But I think that we should use `self.class.default_charset` here.