Implement MediaStreamTrack contentHint skeleton.

third_party/WebKit/Source/modules/mediastream/MediaStreamTrack.h

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2011 Ericsson AB. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 47 matching lines @@
   String kind() const;
   String id() const;
   String label() const;
   bool remote() const;
 
   bool enabled() const;
   void setEnabled(bool);
 
   bool muted() const;
 
+  String contentHint() const;
+  void setContentHint(const String&);
+
   String readyState() const;
 
   void stopTrack(ExceptionState&);
   virtual MediaStreamTrack* clone(ExecutionContext*);
 
   void getConstraints(MediaTrackConstraints&);
 
   // This function is called when constrains have been successfully applied.
   // Called from UserMediaRequest when it succeeds. It is not IDL-exposed.
   void setConstraints(const WebMediaConstraints&);
@@ skipping 40 matching lines @@
   bool m_stopped;
   Member<MediaStreamComponent> m_component;
   WebMediaConstraints m_constraints;
 };
 
 typedef HeapVector<Member<MediaStreamTrack>> MediaStreamTrackVector;
 
 }  // namespace blink
 
 #endif  // MediaStreamTrack_h