Persist offline page info in a navigation entry if needed

components/sessions/core/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_CORE_SERIALIZED_NAVIGATION_DRIVER_H_
 #define COMPONENTS_SESSIONS_CORE_SERIALIZED_NAVIGATION_DRIVER_H_
 
+#include <map>
+#include <memory>
 #include <string>
 
 #include "components/sessions/core/sessions_export.h"
 
+namespace content {
+class NavigationEntry;
+}
+
 namespace sessions {
 
+class ExtendedInfoHandler;
 class SerializedNavigationEntry;
 
 // The SerializedNavigationDriver interface allows SerializedNavigationEntry to
 // obtain information from a singleton driver object. A concrete implementation
 // must be provided by the driver on each platform.
 class SESSIONS_EXPORT SerializedNavigationDriver {
  public:
   virtual ~SerializedNavigationDriver() {}
 
   // Returns the singleton SerializedNavigationDriver.
@@ skipping 19 matching lines @@
   virtual std::string GetSanitizedPageStateForPickle(
       const SerializedNavigationEntry* navigation) const = 0;
 
   // Sanitizes the data in the given |navigation| to be more robust against
   // faulty data written by older versions.
   virtual void Sanitize(SerializedNavigationEntry* navigation) const = 0;
 
   // Removes the referrer from the encoded page state.
   virtual std::string StripReferrerFromPageState(
       const std::string& page_state) const = 0;
+
+  // Registers a handler that is used to read and write the extended
+  // info stored in SerializedNavigationEntry.
+  virtual void RegisterExtendedInfoHandler(

[sky, 2016/09/28 00:22:00]

Can you clarify why you want to add these functions here? The functionality is
content specific and should only be in the content side of things. Unless I'm
missing something you should *not* change this code at all, all your changes
should be in components/sessions/content. These functions should be non-virtual
on ContentSerializedNavigationDriver.

+      const std::string& key,
+      std::unique_ptr<ExtendedInfoHandler> handler) = 0;
+
+  using ExtendedInfoHandlerMap =
+      std::map<std::string, std::unique_ptr<ExtendedInfoHandler>>;
+
+  // Returns all the registered handlers to deal with the extended info.
+  virtual const ExtendedInfoHandlerMap& GetAllExtendedInfoHandlers() const = 0;
 };
 
 }  // namespace sessions
 
 #endif  // COMPONENTS_SESSIONS_CORE_SERIALIZED_NAVIGATION_DRIVER_H_