Persist offline page info in a navigation entry if needed

components/sessions/core/serialized_navigation_entry.h

Index: components/sessions/core/serialized_navigation_entry.h
diff --git a/components/sessions/core/serialized_navigation_entry.h b/components/sessions/core/serialized_navigation_entry.h
index cc3b53d0f29df4d1cca140c959c8aa9b0c3f112e..666738b1e96c83db1f597b048d76bc4c1028dfd8 100644
--- a/components/sessions/core/serialized_navigation_entry.h
+++ b/components/sessions/core/serialized_navigation_entry.h
@@ -7,6 +7,7 @@
 
 #include <stdint.h>
 
+#include <map>
 #include <memory>
 #include <set>
 #include <string>
@@ -123,6 +124,10 @@ class SESSIONS_EXPORT SerializedNavigationEntry {
   }
   const std::vector<GURL>& redirect_chain() const { return redirect_chain_; }
 
+  const std::map<std::string, std::string>& extended_info_map() const {
+    return extended_info_map_;
+  }
+
  private:
   friend class ContentSerializedNavigationBuilder;
   friend class ContentSerializedNavigationDriver;
@@ -156,6 +161,14 @@ class SESSIONS_EXPORT SerializedNavigationEntry {
   BlockedState blocked_state_;
   PasswordState password_state_;
   std::set<std::string> content_pack_categories_;
+
+  // The map that tracks all the extended info that need to be persisted, but
+  // would want to avoid the core session restore to know about the details.
+  // The consumer should implement the ExtendedInfoHandler interface and calls
+  // SerializedNavigationDriver::RegisterExtendedInfoHandler to register it.
+  // Note that all the map data are not synced since the only one added now does
+  // not need it.
+  std::map<std::string, std::string> extended_info_map_;
 };
 
 }  // namespace sessions