Firefox screensharing visible in call but not in stream.

[pierreozoux]

Description

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During a call a person with firefox started sharing her desktop, we could see it in the call, but nothing appeared in the stream.
If you are interested, I can provide you a video of the bug.

Current behavior

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User in firefox, shares screen, doesn't appear on stream.

Expected Behavior

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The screensharing should appear like in the call.

Possible Solution

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Steps to reproduce

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Environment details

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Latest stable build in docker.
I'm asking the user the firefox version.