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

Source/core/html/track/TextTrack.cpp

Index: Source/core/html/track/TextTrack.cpp
diff --git a/Source/core/html/track/TextTrack.cpp b/Source/core/html/track/TextTrack.cpp
index 85c90290d0a837b563cc128742b3846600521393..b195d3ac680e0019fcaa938f79f58500374f4558 100644
--- a/Source/core/html/track/TextTrack.cpp
+++ b/Source/core/html/track/TextTrack.cpp
@@ -146,6 +146,13 @@ bool TextTrack::isValidKindKeyword(const AtomicString& value)
     return false;
 }
 
+void TextTrack::setTrackList(TextTrackList* trackList)
+{
+    m_trackList = trackList;
+    if (!m_trackList && m_cues && m_client)
+        m_client->textTrackRemoveCues(this, m_cues.get());
+}
+
 void TextTrack::setKind(const AtomicString& newKind)
 {
     AtomicString oldKind = kind();
@@ -423,4 +430,3 @@ ExecutionContext* TextTrack::executionContext() const
 }
 
 } // namespace WebCore
-