Media Session API: use MediaMetadata in the browser process.

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 2ad466e0e2e631701882ea9f0c299119f1fd6405..aa480fb1ca01382c7f9dd6506267398f548eef89 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -13,6 +13,7 @@
 #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/security_style.h"
 #include "ipc/ipc_listener.h"
 #include "ipc/ipc_sender.h"
@@ -445,7 +446,8 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
 
   // Invoked when media session has changed its state.
   virtual void MediaSessionStateChanged(bool is_controllable,
-                                        bool is_suspended) {}
+                                        bool is_suspended,
+                                        const MediaMetadata& metadata) {}
 
   // Invoked when the renderer process changes the page scale factor.
   virtual void OnPageScaleFactorChanged(float page_scale_factor) {}