Implement MediaMetadata artwork in content

content/public/common/media_metadata.h

Index: content/public/common/media_metadata.h
diff --git a/content/public/common/media_metadata.h b/content/public/common/media_metadata.h
index 3d7f13c59366caac20a29ed98b79c0d8a8478d58..6cd662ae5ce19eab2ae9f35b6c190f1c1540a160 100644
--- a/content/public/common/media_metadata.h
+++ b/content/public/common/media_metadata.h
@@ -5,17 +5,26 @@
 #ifndef CONTENT_PUBLIC_COMMON_MEDIA_METADATA_H_
 #define CONTENT_PUBLIC_COMMON_MEDIA_METADATA_H_
 
+#include <vector>
+
 #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;
 
@@ -28,11 +37,8 @@ struct CONTENT_EXPORT MediaMetadata {
   // 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