This is as an option to render content with a content type of
`text/plain`. This is the preferred option if you are planning to render
a plain text content.
Please see #12374 for more detail.
This is an option for sending a raw content back to browser. Note that
this rendering option will unset the default content type and does not
include "Content-Type" header back in the response.
You should only use this option if you are expecting the "Content-Type"
header to not be set. More information on "Content-Type" header can be
found on RFC 2616, section 7.2.1.
Please see #12374 for more detail.
