title: How to enable upload in Gecko FX 60?
body: <p>I have developped an application that uses GeckoFX.
  I have recently upgraded from GeckoFX 45 to GeckoFX 60.
  Since the upgrade it is impossble to upload files anymore (The app upload files to AWS either via drag and drop or by selecting the file directly on the computer). It's working fine with GeckoFX 45.
  I've tested the website and it works fine on FF60 so the problem seems to come indeed from GeckoFX 60.
  I've logged the Gecko Console and there is nothing in there.</p>
  <p>Is there some setting (User Preferences) that needs to be set ? Why would this stop working all the sudden after the upgrade to Gecko 60 ?</p>
  <p>What can I do to try and debug this ?</p>
  <p>Thanks in advance.</p>