Fix publications' track property initialization (#867)

The constructors of `LocalTrackPublication` and `RemoteTrackPublication`
relied on setting the `track` property during initialization. However,
because `updateTrack()` was an un-awaited async method, the `track`
property was null immediately after construction, which caused
confusion.

Author: hiroshihorie

lib/src/publication/local.dart

@@ -31,8 +31,7 @@ class LocalTrackPublication<T extends LocalTrack> extends TrackPublication<T> {
     required this.participant,
     required lk_models.TrackInfo info,
     required T track,
-  }) : super(info: info) {
-    updateTrack(track);
+  }) : super(info: info, track: track) {
     // register dispose func
     onDispose(() async {
       // this object is responsible for disposing track

lib/src/publication/remote.dart

@@ -105,7 +105,7 @@ class RemoteTrackPublication<T extends RemoteTrack>
     required this.participant,
     required lk_models.TrackInfo info,
     T? track,
-  }) : super(info: info) {
+  }) : super(info: info, track: track) {
     logger.fine('RemoteTrackPublication.init track: $track, info: $info');
 
     // register dispose func
@@ -121,8 +121,6 @@ class RemoteTrackPublication<T extends RemoteTrack>
       cancelFunc: (func) => _cancelPendingTrackSettingsUpdateRequest = func,
       wait: const Duration(milliseconds: 1500),
     );
-
-    updateTrack(track);
   }
 
   @internal

lib/src/publication/track_publication.dart

@@ -68,13 +68,16 @@ abstract class TrackPublication<T extends Track> extends Disposable {
 
   TrackPublication({
     required lk_models.TrackInfo info,
+    required T? track,
   })  : sid = info.sid,
         name = info.name,
         kind = info.type.toLKType(),
         source = info.source.toLKType(),
         _simulcasted = info.simulcast,
         _metadataMuted = info.muted,
-        _mimeType = info.mimeType {
+        _mimeType = info.mimeType,
+        _track = track {
+    if (track != null) _attachTrackListener(track);
     updateFromInfo(info);
   }
 
@@ -110,19 +113,19 @@ abstract class TrackPublication<T extends Track> extends Disposable {
     // dispose previous track (if exists)
     await _track?.dispose();
     _track = newValue;
-
-    if (newValue != null) {
-      // listen for Track's muted events
-      final listener = newValue.createListener()
-        ..on<InternalTrackMuteUpdatedEvent>(
-            (event) => _onTrackMuteUpdatedEvent(event));
-      // dispose listener when the track is disposed
-      newValue.onDispose(() => listener.dispose());
-    }
+    if (newValue != null) _attachTrackListener(newValue);
 
     return true;
   }
 
+  void _attachTrackListener(T track) {
+    // listen for Track's muted events
+    final listener = track.createListener()
+      ..on<InternalTrackMuteUpdatedEvent>((event) => _onTrackMuteUpdatedEvent(event));
+    // dispose listener when the track is disposed
+    track.onDispose(() => listener.dispose());
+  }
+
   void _onTrackMuteUpdatedEvent(InternalTrackMuteUpdatedEvent event) {
     // send signal to server (if mute initiated by local user)
     if (event.shouldSendSignal) {