Created from https://bugs.chromium.org/p/webrtc/issues/detail?id=6142

Copy of the description:

What steps will reproduce the problem?
1. Go to https://dev-licode1.hirevue.net:3004/ on Chrome 54+
2. Open another tab, and go to the same page

What is the expected result?

user can hear audio from the other tab, and vice-versa.

What do you see instead?

user cannot hear audio from the other tab.  If you open the second tab in Chrome 53 or lower, the Chrome 53 user *will* be able to hear the Chrome 54 user, but the Chrome 54 user cannot hear the Chrome 53 user.  So not a microphone issue, but an output device issue


What version of the product are you using? On what operating system?

Version 54.0.2807.0 canary (64-bit) on OSX 10.9.5

Please provide any additional information below.

This defect is somehow related to a new flag, chrome://flags/#new-audio-rendering-mixing-strategy and the video tag's setSinkId().  If I comment this code out on the page above:

```
    var audioSinkChanged = function(event) {
        that.video.setSinkId(event.sinkId)
            .then(function() {
                L.Logger.info('Success, audio output device attached: ' + event.sinkId + ' to ' + that.id);
            })
            .catch(function(error) {
                L.Logger.error(error);
            });
    };
```

...it does not reproduce.  Likewise, if I disable that new audio mixing mode feature, it does not reproduce.  So some errant interaction between those two features.