This extension is in beta state, please send feedback on your experiences and wishes!
'Modify Content-Type' allows manipulation of the Content-Type and Content-Disposition HTTP header fields of incoming documents. This may be helpful if you like to force the browser to either show a document inside the browser window or to offer it as a download. It also can be used to override unknown mime types sent by misconfigured servers. Just replace them by f.e. 'application/pdf' or 'application/xml' and Chrome will know how to show the document.
– 'Access your data on all websites': required to get access to the http headers of requested documents.
— added support for multiple rules per URL