Wrap MediaMetadata in base::Optional in content and chrome

content/browser/media/android/browser_media_session_manager.h

Index: content/browser/media/android/browser_media_session_manager.h
diff --git a/content/browser/media/android/browser_media_session_manager.h b/content/browser/media/android/browser_media_session_manager.h
index cd92bdc746c8ee029ca3ef3b09c6c4b1cc8da3bb..25cc839030b0128642cf6e68f8b084976659bd16 100644
--- a/content/browser/media/android/browser_media_session_manager.h
+++ b/content/browser/media/android/browser_media_session_manager.h
@@ -8,9 +8,13 @@
 #include "base/macros.h"
 #include "content/common/content_export.h"
 
+namespace base {
+template <typename T> class Optional;
+}  // namespace base
+
 namespace IPC {
 class Message;
-}
+}  // namespace IPC
 
 namespace content {
 
@@ -24,7 +28,8 @@ class CONTENT_EXPORT BrowserMediaSessionManager {
   // Message handlers.
   virtual void OnActivate(int session_id, int request_id);
   virtual void OnDeactivate(int session_id, int request_id);
-  virtual void OnSetMetadata(int session_id, const MediaMetadata& metadata);
+  virtual void OnSetMetadata(
+      int session_id, const base::Optional<MediaMetadata>& metadata);
 
   int GetRoutingID() const;