Media Session API: make MediaMetadata mutable.

third_party/WebKit/Source/modules/mediasession/MediaMetadata.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 MediaMetadata_h
 #define MediaMetadata_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/ModulesExport.h"
+#include "platform/Timer.h"
 #include "platform/heap/Handle.h"
 #include "wtf/text/WTFString.h"
 
 namespace blink {
 
 class ExecutionContext;
 class MediaImage;
 class MediaMetadataInit;
+class MediaSession;
 
 // Implementation of MediaMetadata interface from the Media Session API.
+// The MediaMetadata object is linked to a MediaSession that owns it. When one
+// of its properties are updated, the object will notify its MediaSession if
+// any. The notification will be made asynchronously in order to combine changes
+// made inside the same event loop. When a MediaMetadata is created and assigned
+// to a MediaSession, the MediaSession will automatically update.
 class MODULES_EXPORT MediaMetadata final
     : public GarbageCollectedFinalized<MediaMetadata>,
       public ScriptWrappable {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
   static MediaMetadata* create(ExecutionContext*, const MediaMetadataInit&);
 
   String title() const;
   String artist() const;
   String album() const;
   const HeapVector<Member<MediaImage>>& artwork() const;
 
+  void setTitle(const String&);
+  void setArtist(const String&);
+  void setAlbum(const String&);
+  void setArtwork(const HeapVector<Member<MediaImage>>&);
+
+  // Called by MediaSession to associate or de-associate itself.
+  void setSession(MediaSession*);
+
   DECLARE_VIRTUAL_TRACE();
 
  private:
   MediaMetadata(ExecutionContext*, const MediaMetadataInit&);
 
+  // Called when one of the metadata fields is updated from script. It will
+  // notify the session asynchronously in order to bundle multiple call in one
+  // notification.
+  void notifySessionAsync();
+
+  // Called asynchronously after at least one field of MediaMetadata has been
+  // modified.
+  void notifySessionTimerFired(TimerBase*);
+
   String m_title;
   String m_artist;
   String m_album;
   HeapVector<Member<MediaImage>> m_artwork;
+
+  Member<MediaSession> m_session;
+  Timer<MediaMetadata> m_notifySessionTimer;
 };
 
 }  // namespace blink
 
 #endif  // MediaMetadata_h