Bugzilla

### Beta/Release Uplift Approval Request
* **User impact if declined**: Remote viewers in WebRTC calls may experience seizure-inducing flickering (between two video sources) that won't stop, when a website replaces a video track currently being transmitted with another different video track (without renegotiating) e.g. when a user attempts to switch to another camera or to sharing their screen in place of their camera stream.
* **Is this code covered by automated tests?**: No
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: STRs in comment 0 and comment 7 (see comment 9 on limitations of our automated test).
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: Low risk since patch is small, well-contained and adds code to remove an input that should have been removed, but wasn't for video like it was for audio, because video uses "direct" listeners, a second class of listener plumbing. Now the code removes these "direct" listeners as well, not just the regular ones. These "direct" listeners are and were cleaned up everywhere else, just not in this recently introduced replaceTrack code optimization.
* **String changes made/needed**:

### Beta/Release Uplift Approval Request
* **User impact if declined**: Remote viewers in WebRTC calls may experience seizure-inducing flickering (between two video sources) that won't stop, when a website attempts to replace a video track currently being transmitted with another different video track (without renegotiating) e.g. when a user attempts to switch to another camera or to sharing their screen in place of their camera stream.
* **Is this code covered by automated tests?**: No
* **Has the fix been verified in Nightly?**: Yes
* **Needs manual test from QE?**: Yes
* **If yes, steps to reproduce**: STRs in comment 0 and comment 7 (see comment 9 on limitations of our automated test).
* **List of other uplifts needed**: None
* **Risk to taking this patch**: Low
* **Why is the change risky/not risky? (and alternatives if risky)**: Low risk since patch is small, well-contained and adds code to remove an input that should have been removed, but wasn't for video like it was for audio, because video uses "direct" listeners, a second class of listener plumbing. Now the code removes these "direct" listeners as well, not just the regular ones. These "direct" listeners are and were cleaned up everywhere else, just not in this recently introduced replaceTrack code optimization.
* **String changes made/needed**: