Make calls to AtomicString(const String&) explicit in html/

Source/core/html/track/TextTrackCue.h

Index: Source/core/html/track/TextTrackCue.h
diff --git a/Source/core/html/track/TextTrackCue.h b/Source/core/html/track/TextTrackCue.h
index 1779e37a7d1caae6c88bfe3e3195e3cbfeea8a93..6e9da464f62da307c13f7bfed9f98009ac32a63d 100644
--- a/Source/core/html/track/TextTrackCue.h
+++ b/Source/core/html/track/TextTrackCue.h
@@ -56,8 +56,8 @@ public:
     TextTrack* track() const;
     void setTrack(TextTrack*);
 
-    const String& id() const { return m_id; }
-    void setId(const String&);
+    const AtomicString& id() const { return m_id; }
+    void setId(const AtomicString&);
 
     double startTime() const { return m_startTime; }
     void setStartTime(double, ExceptionState&);
@@ -101,7 +101,7 @@ protected:
     virtual void cueDidChange();
 
 private:
-    String m_id;
+    AtomicString m_id;
     double m_startTime;
     double m_endTime;
     int m_cueIndex;