--- a/dom/media/MediaStreamGraphImpl.h
+++ b/dom/media/MediaStreamGraphImpl.h
@@ -459,21 +459,16 @@ public:
 #ifdef DEBUG
     if (!OnGraphThreadOrNotRunning()) {
       mMonitor.AssertCurrentThreadOwns();
     }
 #endif
     return mDriver;
   }
 
-  bool RemoveMixerCallback(MixerCallbackReceiver* aReceiver)
-  {
-    return mMixer.RemoveCallback(aReceiver);
-  }
-
   /**
    * Effectively set the new driver, while we are switching.
    * It is only safe to call this at the very end of an iteration, when there
    * has been a SwitchAtNextIteration call during the iteration. The driver
    * should return and pass the control to the new driver shortly after.
    * We can also switch from Revive() (on MainThread), in which case the
    * monitor is held
    */