Bug 1764186 - Make sure MediaInputPort::Get{Source, Destination} are graph-thread only r=bwc,padenot

`MediaInputPort::Get{Source, Destination}` should be graph-thread only since the `MediaInputPort`'s `mSource` and `mDest` will be cleaned up on the graph thread [1], in case of causing some potential racing issues.

[1] https://searchfox.org/mozilla-central/rev/10edce3685369a4c73955cc8d5fcbc5a9d7598af/dom/media/MediaTrackGraph.cpp#2944-2945

Differential Revision: https://phabricator.services.mozilla.com/D143780

dom/media/MediaTrackGraph.cpp

@@ -3092,6 +3092,16 @@ void MediaInputPort::Disconnect() {
   mGraph->SetTrackOrderDirty();
 }
 
+MediaTrack* MediaInputPort::GetSource() const {
+  mGraph->AssertOnGraphThreadOrNotRunning();
+  return mSource;
+}
+
+ProcessedMediaTrack* MediaInputPort::GetDestination() const {
+  mGraph->AssertOnGraphThreadOrNotRunning();
+  return mDest;
+}
+
 MediaInputPort::InputInterval MediaInputPort::GetNextInputInterval(
     MediaInputPort const* aPort, GraphTime aTime) {
   InputInterval result = {GRAPH_TIME_MAX, GRAPH_TIME_MAX, false};
@@ -3169,7 +3179,7 @@ already_AddRefed<MediaInputPort> ProcessedMediaTrack::AllocateInputPort(
   class Message : public ControlMessage {
    public:
     explicit Message(MediaInputPort* aPort)
-        : ControlMessage(aPort->GetDestination()), mPort(aPort) {}
+        : ControlMessage(aPort->mDest), mPort(aPort) {}
     void Run() override {
       TRACE("ProcessedMediaTrack::AllocateInputPort ControlMessage");
       mPort->Init();

dom/media/MediaTrackGraph.h

@@ -816,8 +816,8 @@ class MediaInputPort final {
   // and destination tracks.
   void Disconnect();
 
-  MediaTrack* GetSource() const { return mSource; }
-  ProcessedMediaTrack* GetDestination() const { return mDest; }
+  MediaTrack* GetSource() const;
+  ProcessedMediaTrack* GetDestination() const;
 
   uint16_t InputNumber() const { return mInputNumber; }
   uint16_t OutputNumber() const { return mOutputNumber; }

dom/media/webrtc/transportbridge/MediaPipeline.cpp

@@ -879,8 +879,7 @@ void MediaPipelineTransmit::UpdateSendState() {
       mSendTrackOverride.Ref() && !mSendTrackOverride.Ref()->IsDestroyed();
   const bool mustRemoveSendTrack =
       haveLiveSendTrack && !mSendTrackOverride.Ref() &&
-      (!haveLiveDomTrack ||
-       mDomTrack.Ref()->GetTrack() != mSendPort->GetSource());
+      (!haveLiveDomTrack || mDomTrack.Ref()->GetTrack() != mSendPortSource);
 
   mTransmitting = mActive && (haveLiveDomTrack || haveLiveOverrideTrack) &&
                   !mustRemoveSendTrack;
@@ -917,7 +916,8 @@ void MediaPipelineTransmit::UpdateSendState() {
     } else {
       mSendTrack = mDomTrack.Ref()->Graph()->CreateForwardedInputTrack(
           mDomTrack.Ref()->GetTrack()->mType);
-      mSendPort = mSendTrack->AllocateInputPort(mDomTrack.Ref()->GetTrack());
+      mSendPortSource = mDomTrack.Ref()->GetTrack();
+      mSendPort = mSendTrack->AllocateInputPort(mSendPortSource.get());
     }
     mSendTrack->QueueSetAutoend(false);
     if (mIsVideo) {
@@ -948,6 +948,7 @@ void MediaPipelineTransmit::UpdateSendState() {
       mSendTrack->Destroy();
       mSendPort->Destroy();
       mSendPort = nullptr;
+      mSendPortSource = nullptr;
     }
   }
 }

dom/media/webrtc/transportbridge/MediaPipeline.h

@@ -318,6 +318,8 @@ class MediaPipelineTransmit
   Watchable<RefPtr<dom::MediaStreamTrack>> mDomTrack;
   // Input port connecting mDomTrack's MediaTrack to mSendTrack.
   RefPtr<MediaInputPort> mSendPort;
+  // The source track of the mSendTrack. Main thread only.
+  RefPtr<ProcessedMediaTrack> mSendPortSource;
   // True if a parameter affecting mDescription has changed. To avoid updating
   // the description unnecessarily. Main thread only.
   bool mDescriptionInvalidated = true;