Prevent 'removetrack' events from firing when all inband text tracks are removed.

Source/core/html/track/InbandTextTrack.cpp

Index: Source/core/html/track/InbandTextTrack.cpp
diff --git a/Source/core/html/track/InbandTextTrack.cpp b/Source/core/html/track/InbandTextTrack.cpp
index 925f84e7c9d7141624825dac3bc838a1d815b73a..29ac326b328e593f41c02c890d5386856008bcbf 100644
--- a/Source/core/html/track/InbandTextTrack.cpp
+++ b/Source/core/html/track/InbandTextTrack.cpp
@@ -84,8 +84,12 @@ size_t InbandTextTrack::inbandTrackIndex()
     return m_webTrack->textTrackIndex();
 }
 
-void InbandTextTrack::trackRemoved()
+void InbandTextTrack::setTrackList(TextTrackList* trackList)
 {
+    TextTrack::setTrackList(trackList);
+    if (trackList)
+        return;
+
     ASSERT(m_webTrack);
     m_webTrack->setClient(0);
     m_webTrack = 0;