Do not let go of MediaStreamTracks too early.

third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.cpp

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2011 Ericsson AB. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 192 matching lines @@
     for (HeapHashSet<Member<MediaStream>>::iterator iter = m_registeredMediaStreams.begin(); iter != m_registeredMediaStreams.end(); ++iter)
         (*iter)->trackEnded();
     m_isIteratingRegisteredMediaStreams = false;
 }
 
 void MediaStreamTrack::stop()
 {
     m_stopped = true;
 }
 
+bool MediaStreamTrack::hasPendingActivity() const
+{
+    return !m_stopped && hasEventListeners();

[sof, 2016/02/07 06:54:27]

I wonder if something effectively like this needs to be done for all
ActiveDOMObjects? It isn't done for several.

[sof, 2016/02/07 07:04:36]

I notice MajorGCWrapperVisitor has special handling for Nodes with event
listeners, but not ActiveDOMObjects.

[haraken, 2016/02/07 07:21:31]

Yeah, without having the check, we'll end up with keeping ActiveDOMObjects alive
longer than needed. So we should.

That said, we can't simply check hasEventListeners in V8GCController because
each ActiveDOMObject has its own semantics to keep the object alive. So I think
we need to manually add the hasEventListeners check to all
hasPendingActivity()'s that need the check.

+}
+
 PassOwnPtr<AudioSourceProvider> MediaStreamTrack::createWebAudioSource()
 {
     return MediaStreamCenter::instance().createWebAudioSourceFromMediaStreamTrack(component());
 }
 
 void MediaStreamTrack::registerMediaStream(MediaStream* mediaStream)
 {
     RELEASE_ASSERT(!m_isIteratingRegisteredMediaStreams);
     RELEASE_ASSERT(!m_registeredMediaStreams.contains(mediaStream));
     m_registeredMediaStreams.add(mediaStream);
@@ skipping 19 matching lines @@
 
 DEFINE_TRACE(MediaStreamTrack)
 {
     visitor->trace(m_registeredMediaStreams);
     visitor->trace(m_component);
     RefCountedGarbageCollectedEventTargetWithInlineData<MediaStreamTrack>::trace(visitor);
     ActiveDOMObject::trace(visitor);
 }
 
 } // namespace blink