Adding mojo MediaSessionClient to support media controls

content/browser/media/session/media_session_service_impl.h

Index: content/browser/media/session/media_session_service_impl.h
diff --git a/content/browser/media/session/media_session_service_impl.h b/content/browser/media/session/media_session_service_impl.h
index ec737024ab9b7160ba6a3a77c5d5a1ee065b04c8..9ecc567318fa551269d23d5cd27cd2225f55b050 100644
--- a/content/browser/media/session/media_session_service_impl.h
+++ b/content/browser/media/session/media_session_service_impl.h
@@ -25,9 +25,14 @@ class MediaSessionServiceImpl : public blink::mojom::MediaSessionService {
  private:
   explicit MediaSessionServiceImpl(RenderFrameHost* render_frame_host);
 
+  void SetClient(blink::mojom::MediaSessionClientPtr client) override;
+
   void SetMetadata(
       const base::Optional<content::MediaMetadata>& metadata) override;
 
+  void DidSetEventHandlerForAction(const std::string& action,
+                                   bool is_set) override;
+
   void Bind(blink::mojom::MediaSessionServiceRequest request);
 
   RenderFrameHost* render_frame_host_;
@@ -35,6 +40,7 @@ class MediaSessionServiceImpl : public blink::mojom::MediaSessionService {
   // RAII binding of |this| to an MediaSessionService interface request.
   // The binding is removed when binding_ is cleared or goes out of scope.
   std::unique_ptr<mojo::Binding<blink::mojom::MediaSessionService>> binding_;
+  blink::mojom::MediaSessionClientPtr client_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaSessionServiceImpl);
 };