Link MediaSessionTabHelper with native MediaSession [CL is going to be split]

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 704c509ca61dde486397478d641fd8c438bfc1cc..b73f072523bcf46a03904c3c3c36275cd17434b3 100644
--- a/content/public/browser/web_contents_observer.h
+++ b/content/public/browser/web_contents_observer.h
@@ -38,7 +38,6 @@ struct AXLocationChangeNotificationDetails;
 struct FaviconURL;
 struct FrameNavigateParams;
 struct LoadCommittedDetails;
-struct MediaMetadata;
 struct Referrer;
 struct ResourceRedirectDetails;
 struct ResourceRequestDetails;
@@ -468,15 +467,6 @@ class CONTENT_EXPORT WebContentsObserver : public IPC::Listener,
   virtual void MediaStartedPlaying(const MediaPlayerId& id) {}
   virtual void MediaStoppedPlaying(const MediaPlayerId& id) {}
 
-  // Invoked when media session has changed its state.
-  virtual void MediaSessionStateChanged(bool is_controllable,
-                                        bool is_suspended) {}
-
-  // Invoked when media session metadata has changed. When |metadata| is
-  // nullopt, it means the metadata is being unset.
-  virtual void MediaSessionMetadataChanged(
-      const base::Optional<MediaMetadata>& metadata) {}
-
   // Invoked when the renderer process changes the page scale factor.
   virtual void OnPageScaleFactorChanged(float page_scale_factor) {}