class ActiveSupport::JSON::Encoding::JSONGemEncoder::EscapedString

def to_json(*)

:nodoc:
This class wraps all the strings we see and does the extra escaping 
def to_json(*)
  if Encoding.escape_html_entities_in_json
    s = super
    s.gsub! ESCAPE_REGEX_WITH_HTML_ENTITIES, ESCAPED_CHARS
    s
  else
    s = super
    s.gsub! ESCAPE_REGEX_WITHOUT_HTML_ENTITIES, ESCAPED_CHARS
    s
  end
end