Wrap MediaMetadata in base::Optional in content and chrome

content/public/browser/web_contents_observer.h

Index: content/public/browser/web_contents_observer.h
diff --git a/content/public/browser/web_contents_observer.h b/content/public/browser/web_contents_observer.h
index e2c42d0eefd9afc07bb09af1a0415f35dff06e6e..09e12707bb7dcb13e7b809dc376006d361095d2c 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -13,7 +13,6 @@
 #include "content/common/content_export.h"
 #include "content/public/browser/navigation_controller.h"
 #include "content/public/common/frame_navigate_params.h"
-#include "content/public/common/media_metadata.h"
 #include "content/public/common/resource_type.h"
 #include "content/public/common/security_style.h"
 #include "ipc/ipc_listener.h"
@@ -23,6 +22,10 @@
 #include "ui/base/page_transition_types.h"
 #include "ui/base/window_open_disposition.h"
 
+namespace base {
+template <typename T> class Optional;
+}  // namespace base
+
 namespace content {
 
 class NavigationEntry;
@@ -37,6 +40,7 @@ struct AXLocationChangeNotificationDetails;
 struct FaviconURL;
 struct FrameNavigateParams;
 struct LoadCommittedDetails;
+struct MediaMetadata;
 struct Referrer;
 struct ResourceRedirectDetails;
 struct ResourceRequestDetails;
@@ -469,9 +473,10 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   virtual void MediaStoppedPlaying(const MediaPlayerId& id) {}
 
   // Invoked when media session has changed its state.
-  virtual void MediaSessionStateChanged(bool is_controllable,
-                                        bool is_suspended,
-                                        const MediaMetadata& metadata) {}
+  virtual void MediaSessionStateChanged(
+      bool is_controllable,
+      bool is_suspended,
+      const base::Optional<MediaMetadata>& metadata) {}
 
   // Invoked when the renderer process changes the page scale factor.
   virtual void OnPageScaleFactorChanged(float page_scale_factor) {}