Refactors offline page tab helper to stash the offline page item on redirect.

components/offline_pages/offline_page_item.h

 // Copyright 2015 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_OFFLINE_PAGES_OFFLINE_PAGE_ITEM_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ITEM_H_
 
 #include <stdint.h>
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/strings/string16.h"
+#include "base/supports_user_data.h"
 #include "base/time/time.h"
 #include "url/gurl.h"
 
 namespace offline_pages {
 
 struct ClientId {
   // The namespace for the id (of course 'namespace' is a reserved word, so...)
   std::string name_space;
   // The id in the client's namespace.  Opaque to us.
   std::string id;
 
   ClientId();
   ClientId(std::string name_space, std::string id);
 
   bool operator==(const ClientId& client_id) const;
 };
 
 // Metadata of the offline page.
-struct OfflinePageItem {
+struct OfflinePageItem : public base::SupportsUserData::Data {
  public:
   // Note that this should match with Flags enum in offline_pages.proto.
   enum Flags {
     NO_FLAG = 0,
     MARKED_FOR_DELETION = 0x1,
   };
 
   OfflinePageItem();
   OfflinePageItem(const GURL& url,
                   int64_t offline_id,
                   const ClientId& client_id,
                   const base::FilePath& file_path,
                   int64_t file_size);
   OfflinePageItem(const GURL& url,
                   int64_t offline_id,
                   const ClientId& client_id,
                   const base::FilePath& file_path,
                   int64_t file_size,
                   const base::Time& creation_time);
   OfflinePageItem(const OfflinePageItem& other);
-  ~OfflinePageItem();
+  ~OfflinePageItem() override;
 
   // Gets a URL of the file under |file_path|.
   GURL GetOfflineURL() const;
 
   // Returns whether the offline page is expired.
   bool IsExpired() const;
 
   // The URL of the page.
   GURL url;
   // The primary key/ID for this page in offline pages internal database.
@@ skipping 18 matching lines @@
   base::Time expiration_time;
   // Number of times that the offline archive has been accessed.
   int access_count;
   // Flags about the state and behavior of the offline page.
   Flags flags;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_ITEM_H_