MediaStream API: Adding missing observer calls for remote tracks

Source/modules/mediastream/MediaStream.cpp

Index: Source/modules/mediastream/MediaStream.cpp
diff --git a/Source/modules/mediastream/MediaStream.cpp b/Source/modules/mediastream/MediaStream.cpp
index 1d7b1c133fd51208ba09d3710d79dc04fa59cb11..af0bb6324e06a5e1d5ec85e4acc6d8cd766a3e72 100644
--- a/Source/modules/mediastream/MediaStream.cpp
+++ b/Source/modules/mediastream/MediaStream.cpp
@@ -326,6 +326,7 @@ void MediaStream::addRemoteTrack(MediaStreamComponent* component)
         m_videoTracks.append(track);
         break;
     }
+    track->addObserver(this);
     m_descriptor->addComponent(component);
 
     scheduleDispatchEvent(MediaStreamTrackEvent::create(EventTypeNames::addtrack, false, false, track));
@@ -359,6 +360,7 @@ void MediaStream::removeRemoteTrack(MediaStreamComponent* component)
     m_descriptor->removeComponent(component);
 
     RefPtr<MediaStreamTrack> track = (*tracks)[index];
+    track->removeObserver(this);
     tracks->remove(index);
     scheduleDispatchEvent(MediaStreamTrackEvent::create(EventTypeNames::removetrack, false, false, track));
 }