[GStreamer] notifyPlayerOfTrack: valid existing tracks are purged

https://bugs.webkit.org/show_bug.cgi?id=268001

Reviewed by Xabier Rodriguez-Calvar.

Append stream IDs to validStreams before testing if its track is already
existing to make sure it is added either way.

* Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp:
(WebCore::MediaPlayerPrivateGStreamer::notifyPlayerOfTrack):

Canonical link: https://commits.webkit.org/273492@main

Author: vivienne-w

Source/WebCore/platform/graphics/gstreamer/MediaPlayerPrivateGStreamer.cpp

@@ -1067,6 +1067,7 @@ void MediaPlayerPrivateGStreamer::notifyPlayerOfTrack()
             continue;
 
         AtomString streamId(TrackPrivateBaseGStreamer::trackIdFromPadStreamStartOrUniqueID(type, i, pad));
+        validStreams.append(streamId);
 
         if (i < tracks.size()) {
             RefPtr<TrackPrivateType> existingTrack = tracks.get(streamId);
@@ -1082,7 +1083,6 @@ void MediaPlayerPrivateGStreamer::notifyPlayerOfTrack()
 
         auto track = TrackPrivateType::create(*this, i, GRefPtr(pad));
         ASSERT(track->id() == streamId);
-        validStreams.append(track->id());
         if (!track->trackIndex() && (type == TrackType::Audio || type == TrackType::Video))
             track->setActive(true);
         ASSERT(streamId == track->id());