[oilpan] Figure out lifetime of remaining Node raw pointers (Part 2)

Source/core/html/track/TextTrackList.h

Index: Source/core/html/track/TextTrackList.h
diff --git a/Source/core/html/track/TextTrackList.h b/Source/core/html/track/TextTrackList.h
index 457d322ab83648b15e5326408ae413a899c15588..87f2548c4550ace8ca494176706eb6e0b5811a9e 100644
--- a/Source/core/html/track/TextTrackList.h
+++ b/Source/core/html/track/TextTrackList.h
@@ -98,6 +98,8 @@ private:
     // FIXME(oilpan): This is a weak pointer.
     ScriptExecutionContext* m_context;
     // FIXME(oilpan): This is a strong pointer.
+    // TextTrackList and HTMLMediaElement should die together.
+    // See comment #18 of https://codereview.chromium.org/23451042/ for more details.
     HTMLMediaElement* m_owner;
 
     Vector<RefPtr<Event> > m_pendingEvents;