How can I detect the current tab's mime type in a Mozilla Firefox extension?

Question

I'm trying to do the same thing as asked in this question here, the only signification difference being the use of Mozilla Firefox instead of Google Chrome / Chromium .

I've tried using the Mozilla JetPack SDK and so far, for all content loaded with Mozilla's pdf.js viewer seems to be read as text/html . Is there a correct way to do this using Jetpack (or even XUL) in Firefox ?

Answer 1

I think you can detect a pdf rendered with pdf.js by checking if the document.baseURI property is set to "resource://pdf.js/web/"