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..3a07cc00fe83b62debd3f964f459e96a50cdf606 100644
--- a/components/sessions/content/content_serialized_navigation_driver.h
+++ b/components/sessions/content/content_serialized_navigation_driver.h
@@ -7,6 +7,8 @@
 
 #include "components/sessions/core/serialized_navigation_driver.h"
 
+#include <map>
+
 #include "components/sessions/core/sessions_export.h"
 
 namespace base {
@@ -15,6 +17,8 @@ template <typename T> struct DefaultSingletonTraits;
 
 namespace sessions {
 
+class ExtendedInfoHandler;
+
 // Provides an implementation of SerializedNavigationDriver that is backed by
 // content classes.
 class SESSIONS_EXPORT ContentSerializedNavigationDriver
@@ -38,9 +42,23 @@ class SESSIONS_EXPORT ContentSerializedNavigationDriver
   std::string StripReferrerFromPageState(
       const std::string& page_state) const override;
 
+  // Registers a handler that is used to read and write the extended
+  // info stored in SerializedNavigationEntry.

[sky, 2016/09/29 03:08:19]

Also add 'As part of serialization |key| is written to disk, as such once a
handler is registered it should always be registered to the same key.'

[jianli, 2016/09/29 22:02:29]

Done.

+  void RegisterExtendedInfoHandler(
+      const std::string& key,
+      std::unique_ptr<ExtendedInfoHandler> handler);
+
+  using ExtendedInfoHandlerMap =
+      std::map<std::string, std::unique_ptr<ExtendedInfoHandler>>;
+
+  // Returns all the registered handlers to deal with the extended info.
+  const ExtendedInfoHandlerMap& GetAllExtendedInfoHandlers() const;
+
  private:
   ContentSerializedNavigationDriver();
   friend struct base::DefaultSingletonTraits<ContentSerializedNavigationDriver>;
+
+  ExtendedInfoHandlerMap extended_info_handler_map_;
 };
 
 }  // namespace sessions