Wrap MediaMetadata in base::Optional in content and chrome

content/renderer/media/android/renderer_media_session_manager.h

Index: content/renderer/media/android/renderer_media_session_manager.h
diff --git a/content/renderer/media/android/renderer_media_session_manager.h b/content/renderer/media/android/renderer_media_session_manager.h
index fbfd5c848b057fd027094c836f0634c8748acfca..d081e1b026c6a27e200b1daed5b96482427e5025 100644
--- a/content/renderer/media/android/renderer_media_session_manager.h
+++ b/content/renderer/media/android/renderer_media_session_manager.h
@@ -10,6 +10,7 @@
 
 #include "base/id_map.h"
 #include "base/macros.h"
+#include "base/optional.h"
 #include "content/common/content_export.h"
 #include "content/public/renderer/render_frame_observer.h"
 #include "third_party/WebKit/public/platform/modules/mediasession/WebMediaSession.h"
@@ -36,7 +37,8 @@ class CONTENT_EXPORT RendererMediaSessionManager : public RenderFrameObserver {
   void Deactivate(
       int session_id,
       std::unique_ptr<blink::WebMediaSessionDeactivateCallback> callback);
-  void SetMetadata(int session_id, const MediaMetadata& metadata);
+  void SetMetadata(
+      int session_id, const base::Optional<MediaMetadata>& metadata);
 
   void OnDidActivate(int request_id, bool success);
   void OnDidDeactivate(int request_id);