test.webrtc.org

use firefox2 to open http://test.webrtc.org

 
then click Right-top: START, will get below:

Then to disable the playback device as below:
 
make sure you get:
 
 
then refresh 

http://test.webrtc.org  on FF52:

you will get below, and on UI popup to let the user to Allow. 
And close FF, restart FF, FF background process will not be closed.
like:

 

 
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