[Galene] Experimental outbound activity detection

[Galene] Experimental outbound activity detection

[Alexander Dietrich]

Hello,

I was trying to understand what's missing for outbound activity 
detection (aka "Is this thing on?"), and learned that there is a 
"totalAudioEnergy" property for outgoing WebRTC streams as well, but 
it's not yet implemented in Firefox: 
https://developer.mozilla.org/en-US/docs/Web/API/RTCAudioSourceStats/totalAudioEnergy

It does seem to work in Chromium, using largely the existing code. 
Here's an experimental branch, please let me know what you think: 
https://github.com/jech/galene/compare/master...alxndr42:galene:outbound-activity

There is ongoing work around RTCAudioSourceStats in Firefox, but it's 
not clear to me if and when "totalAudioEnergy" might appear: 
https://bugzilla.mozilla.org/show_bug.cgi?id=1728364

So right now the code detects no activity in Firefox, but "should" start 
to work if they eventually implement the missing parts.

Kind regards,
Alexander