For some reason, https://bugzilla.mozilla.org/show_bug.cgi?id=1167053 changed methods of `NetUtil` yet *again*. This patch thus attempts to handle those changes, while keeping the addon backwards compatible. I've tested this using all current Firefox versions (Nightly, Aurora/DevEdition, Beta, Release, ESR), and things still appears to work correctly.
This is the pdf.js project output, https://github.com/mozilla/pdf.js Current extension version is: PDFJSSCRIPT_VERSION