I have a webrequest of the form: http://localhost/wiki/load.php?debug=true&lang=en&modules=mediawiki.legacy.commonPrint&only=styles&skin=vector
This has the Content-Type for CSS.
When I reload my page, the same request responds with a 304 Not Modified. In this case the content-type is stripped from the response header, because per http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html such responses do not have a content-type.
The inspector reports in this case: "Resource interpreted as script but transferred with MIME type text/php.", whereas it should assume the content-type of the earlier request, it apparently is assuming the content-type of the file extension.
I can confirm the presence of this issue but do not have permission to update the bug's status. In my case I was using a Python-generated CSS.
Created attachment 88040 [details]
[PATCH] Suggested fix
Committing to http://svn.webkit.org/repository/webkit/trunk ...
http://trac.webkit.org/changeset/82822 might have broken Leopard Intel Debug (Tests)
The following tests are not passing: