Implement MediaMetadata artwork in content

content/public/common/media_metadata.h

 // Copyright 2016 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 CONTENT_PUBLIC_COMMON_MEDIA_METADATA_H_
 #define CONTENT_PUBLIC_COMMON_MEDIA_METADATA_H_
 
+#include <vector>
+
+#include "base/optional.h"

[dcheng, 2016/07/07 01:35:53]

Nit: remove unused include

 #include "base/strings/string16.h"
 #include "content/common/content_export.h"
+#include "content/public/common/manifest.h"
 
 namespace content {
 
 // The MediaMetadata is a structure carrying information associated to a
 // content::MediaSession.
 struct CONTENT_EXPORT MediaMetadata {
+  // TODO(zqzhang): move |Manifest::Icon| to a common place. See
+  // https://crbug.com/621859.
+  using Artwork = Manifest::Icon;
+
   MediaMetadata();
   ~MediaMetadata();
 
+  MediaMetadata(const MediaMetadata& other);
+
   bool operator==(const MediaMetadata& other) const;
   bool operator!=(const MediaMetadata& other) const;
 
   // Title associated to the MediaSession.
   base::string16 title;
 
   // Artist associated to the MediaSession.
   base::string16 artist;
 
   // Album associated to the MediaSession.
   base::string16 album;
 
-  // Maximum length for all the strings inside the MediaMetadata when it is sent
-  // over IPC. The renderer process should truncate the strings before sending
-  // the MediaMetadata and the browser process must do the same when receiving
-  // it.
-  static const size_t kMaxIPCStringLength;
+  // Artwork associated to the MediaSession.
+  std::vector<Artwork> artwork;
 };
 
 }  // namespace content
 
 #endif // CONTENT_PUBLIC_COMMON_MEDIA_METADATA_H_