[Video] Add dummy video/audio tracks inactive to select them later.

third_party/WebKit/Source/core/html/HTMLMediaElement.h

 /*
  * Copyright (C) 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. 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 76 matching lines @@
 
  public:
   static MIMETypeRegistry::SupportsType supportsType(const ContentType&);
 
   enum class RecordMetricsBehavior { DoNotRecord, DoRecord };
 
   static void setMediaStreamRegistry(URLRegistry*);
   static bool isMediaStreamURL(const String& url);
   static bool isHLSURL(const KURL&);
 
+  // If HTMLMediaElement is using MediaTracks (either placeholder or provided
+  // by the page).
+  static bool mediaTracksEnabledInternally();
+
   DECLARE_VIRTUAL_TRACE();
 
   DECLARE_VIRTUAL_TRACE_WRAPPERS();
 
   void clearWeakMembers(Visitor*);
   WebMediaPlayer* webMediaPlayer() const { return m_webMediaPlayer.get(); }
 
   // Returns true if the loaded media has a video track.
   // Note that even an audio element can have video track in cases such as
   // <audio src="video.webm">, in which case this function will return true.
@@ skipping 634 matching lines @@
 
 inline bool isHTMLMediaElement(const HTMLElement& element) {
   return isHTMLAudioElement(element) || isHTMLVideoElement(element);
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(HTMLMediaElement);
 
 }  // namespace blink
 
 #endif  // HTMLMediaElement_h