Allow MediaSession in iframes to be routed

content/browser/media/session/media_session_player_observer.h

Index: content/browser/media/session/media_session_player_observer.h
diff --git a/content/browser/media/session/media_session_player_observer.h b/content/browser/media/session/media_session_player_observer.h
index 95ba2613b53c3f2a3b85fd76a504db4fd4451206..66439e447cb1f1de41f69ce73d7955b1074b9736 100644
--- a/content/browser/media/session/media_session_player_observer.h
+++ b/content/browser/media/session/media_session_player_observer.h
@@ -7,6 +7,8 @@
 
 namespace content {
 
+class RenderFrameHost;
+
 class MediaSessionPlayerObserver {
  public:
   MediaSessionPlayerObserver() = default;
@@ -22,6 +24,10 @@ class MediaSessionPlayerObserver {
   // the MediaSession.
   virtual void OnSetVolumeMultiplier(int player_id,
                                      double volume_multiplier) = 0;
+
+  // Returns the RenderFrameHost this player observer belongs to. Returns
+  // nullptr if unavailable.
+  virtual RenderFrameHost* GetRenderFrameHost() const = 0;
 };
 
 }  // namespace content