When Firefox needs some permissions (eg. access to storage to upload files, microphone for WebRTC and so on) and that it doesn't have nor get the permission, it should drop a message in the logcat. The problem that was encountered is a picture hosting platform silently failing to upload files due to missing permission, but no popup appeared, and there was nothing about that missing permission in logcat, leading to a lot of lost time looking for the issue. The problem about permissions that never were asked is filed against bug 1390261.
One problem is that we don't immediately know all of the places where things fail due to an Android permissions issue. In your case, we simply failed to open the file. It's difficult to know that it was due to an Android permissions issue. There would've been an error reported in JS, but none of the web apps you were using surfaced that. Still, in places where we know we failed due to a permissions problem we should print something.
Re-triaging per https://bugzilla.mozilla.org/show_bug.cgi?id=1473195 Needinfo :susheel if you think this bug should be re-triaged.
Priority: P3 → P5
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