Remove internal uses of TrackDisplayUpdateScope in CueTimeline

Source/core/html/track/CueTimeline.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CueTimeline_h
 #define CueTimeline_h
 
 #include "core/html/track/TextTrackCue.h"
 #include "core/html/track/vtt/VTTCue.h"
 #include "platform/PODIntervalTree.h"
@@ skipping 26 matching lines @@
     void beginIgnoringUpdateRequests();
     void endIgnoringUpdateRequests();
 
     CueList currentlyActiveCues() const { return m_currentlyActiveCues; }
 
     DECLARE_TRACE();
 
 private:
     HTMLMediaElement& mediaElement() const { return *m_mediaElement; }
 
+    void addCueInternal(PassRefPtrWillBeRawPtr<TextTrackCue>);
+    void removeCueInternal(PassRefPtrWillBeRawPtr<TextTrackCue>);
+
     RawPtrWillBeMember<HTMLMediaElement> m_mediaElement;
 
     CueIntervalTree m_cueTree;
 
     CueList m_currentlyActiveCues;
     double m_lastUpdateTime;
 
     int m_ignoreUpdate;
 };
 
@@ skipping 30 matching lines @@
     static String string(TextTrackCue* const& cue)
     {
         return cue->toString();
     }
 };
 #endif
 
 } // namespace blink
 
 #endif // CueTimeline_h