Persist offline page info in a navigation entry if needed

components/sessions/content/content_serialized_navigation_driver.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_SESSIONS_CONTENT_CONTENT_SERIALIZED_NAVIGATION_DRIVER_H_
 #define COMPONENTS_SESSIONS_CONTENT_CONTENT_SERIALIZED_NAVIGATION_DRIVER_H_
 
 #include "components/sessions/core/serialized_navigation_driver.h"
 
+#include <map>
+
 #include "components/sessions/core/sessions_export.h"
 
 namespace base {
 template <typename T> struct DefaultSingletonTraits;
 }
 
 namespace sessions {
 
+class ExtendedInfoHandler;
+
 // Provides an implementation of SerializedNavigationDriver that is backed by
 // content classes.
 class SESSIONS_EXPORT ContentSerializedNavigationDriver
     : public SerializedNavigationDriver {
  public:
   ~ContentSerializedNavigationDriver() override;
 
   // Returns the singleton ContentSerializedNavigationDriver.  Almost all
   // callers should use SerializedNavigationDriver::Get() instead.
   static ContentSerializedNavigationDriver* GetInstance();
 
   // SerializedNavigationDriver implementation.
   int GetDefaultReferrerPolicy() const override;
   bool MapReferrerPolicyToOldValues(int referrer_policy,
                                     int* mapped_referrer_policy) const override;
   bool MapReferrerPolicyToNewValues(int referrer_policy,
                                     int* mapped_referrer_policy) const override;
   std::string GetSanitizedPageStateForPickle(
       const SerializedNavigationEntry* navigation) const override;
   void Sanitize(SerializedNavigationEntry* navigation) const override;
   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
 
 #endif  // COMPONENTS_SESSIONS_CONTENT_CONTENT_SERIALIZED_NAVIGATION_DRIVER_H_