Persist offline page info in a navigation entry if needed

content/browser/frame_host/navigation_entry_impl.h

 // Copyright 2013 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 CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_IMPL_H_
 #define CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_IMPL_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 127 matching lines @@
   void SetExtraData(const std::string& key,
                     const base::string16& data) override;
   bool GetExtraData(const std::string& key,
                     base::string16* data) const override;
   void ClearExtraData(const std::string& key) override;
   void SetHttpStatusCode(int http_status_code) override;
   int GetHttpStatusCode() const override;
   void SetRedirectChain(const std::vector<GURL>& redirects) override;
   const std::vector<GURL>& GetRedirectChain() const override;
   bool IsRestored() const override;
+  std::string GetExtraHeaders() const override;
 
   // Creates a copy of this NavigationEntryImpl that can be modified
   // independently from the original.  Does not copy any value that would be
   // cleared in ResetForCommit.  Unlike |CloneAndReplace|, this does not check
   // whether the subframe history items are for frames that are still in the
   // current page.
   std::unique_ptr<NavigationEntryImpl> Clone() const;
 
   // Like |Clone|, but replaces the FrameNavigationEntry corresponding to
   // |target_frame_tree_node| with |frame_entry|, clearing all of its children
@@ skipping 364 matching lines @@
   // persisted, unless specific data is taken out/put back in at save/restore
   // time (see TabNavigation for an example of this).
   std::map<std::string, base::string16> extra_data_;
 
   DISALLOW_COPY_AND_ASSIGN(NavigationEntryImpl);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_FRAME_HOST_NAVIGATION_ENTRY_IMPL_H_