```
$ http_proxy=localhost:8051 curl http://customhostheader.example.com/map_origin_host_header.html
<!--
    This test only works if we've successfully origin-mapped with an
    explicit host header of customhostheader.example.com, which places
    DocumentRoot at /mod_pagespeed_test.
-->
<img src="http://sharedcdn.example.com/test/small.png"/>
```