Bug 1621596 - Adjust one patch from bug 1598114 to land what was meant to be landing

Differential Revision: https://phabricator.services.mozilla.com/D66382

--HG--
extra : moz-landing-system : lando

dom/media/webaudio/AudioEventTimeline.cpp

@@ -101,13 +101,6 @@ AudioTimelineEvent::AudioTimelineEvent(const AudioTimelineEvent& rhs) {
 }
 
 AudioTimelineEvent::~AudioTimelineEvent() {
-  // AudioTimelineEvent can be destroyed on the render thread. If an event
-  // contains an AudioNodeTrack, it means that this AudioNodeTrack can be
-  // destroyed on the render thread. This in turns can provoke a GC, since it
-  // can be the last reference to GC-able objects. We want to avoid causing GC
-  // on the render thread, so mTrack never points to a valid AudioNodeTrack on
-  // destruction, on the render thread.
-  MOZ_ASSERT(NS_IsMainThread() || !mTrack, "Track reference on the render thread should have been dropped when inserting the event in the timeline.");
   if (mType == AudioTimelineEvent::SetValueCurve) {
     delete[] mCurve;
   }

dom/media/webaudio/AudioParamTimeline.h

@@ -42,13 +42,13 @@ class AudioParamTimeline : public AudioEventTimeline {
   }
 
   template <typename TimeType>
-  void InsertEvent(AudioTimelineEvent& aEvent) {
+  void InsertEvent(const AudioTimelineEvent& aEvent) {
     if (aEvent.mType == AudioTimelineEvent::Cancel) {
       CancelScheduledValues(aEvent.Time<TimeType>());
       return;
     }
     if (aEvent.mType == AudioTimelineEvent::Track) {
-      mTrack = aEvent.mTrack.forget();
+      mTrack = aEvent.mTrack;
       return;
     }
     if (aEvent.mType == AudioTimelineEvent::SetValue) {