that we kick off the filter stack with our cache_out filter being the
  first in the chain. This make sense because we want to restore things
  in the same manner as we saved them.
  There may be filters before our cache_out filter, because

  1. We call ap_set_content_type during cache_select. This causes
     Content-Type specific filters to be added.
  2. We call the insert_filter hook. This causes filters e.g. like
     the ones set with SetOutputFilter to be added.

PR: 40090


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@425787 13f79535-47bb-0310-9956-ffa450edef68