Persist offline page info in a navigation entry if needed

components/sessions/content/content_serialized_navigation_driver.h

Index: components/sessions/content/content_serialized_navigation_driver.h
diff --git a/components/sessions/content/content_serialized_navigation_driver.h b/components/sessions/content/content_serialized_navigation_driver.h
index c0911d70e87bd0f102fc689703f557e2349bb382..fd55e16db8ae8bc09097ca0823704a0ef96cd2dc 100644
--- a/components/sessions/content/content_serialized_navigation_driver.h
+++ b/components/sessions/content/content_serialized_navigation_driver.h
@@ -7,6 +7,7 @@
 
 #include "components/sessions/core/serialized_navigation_driver.h"
 
+#include "components/sessions/content/extended_info_handler.h"
 #include "components/sessions/core/sessions_export.h"
 
 namespace base {
@@ -37,10 +38,16 @@ class SESSIONS_EXPORT ContentSerializedNavigationDriver
   void Sanitize(SerializedNavigationEntry* navigation) const override;
   std::string StripReferrerFromPageState(
       const std::string& page_state) const override;
+  void RegisterExtendedInfoHandler(
+      const std::string& key,
+      std::unique_ptr<ExtendedInfoHandler> handler) override;
+  const ExtendedInfoHandlerMap& GetAllExtendedInfoHandlers() const override;
 
  private:
   ContentSerializedNavigationDriver();
   friend struct base::DefaultSingletonTraits<ContentSerializedNavigationDriver>;
+
+  ExtendedInfoHandlerMap extended_info_handler_map_;
 };
 
 }  // namespace sessions