[Offline pages] Fixing a crash in URL change, when offline copy not present

components/offline_pages/offline_page_model.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_MODEL_H_
 #define COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_H_
 
 #include <map>
 #include <vector>
 
@@ skipping 183 matching lines @@
   // observers.
   void CheckForExternalFileDeletion();
 
   // Methods for testing only:
   OfflinePageMetadataStore* GetStoreForTesting();
 
   bool is_loaded() const { return is_loaded_; }
 
  private:
   FRIEND_TEST_ALL_PREFIXES(OfflinePageModelTest, MarkPageForDeletion);
+  FRIEND_TEST_ALL_PREFIXES(OfflinePageModelTest, BookmarkNodeChangesUrl);
 
   typedef ScopedVector<OfflinePageArchiver> PendingArchivers;
 
   // BaseBookmarkModelObserver:
   void BookmarkModelChanged() override;
   void BookmarkNodeAdded(bookmarks::BookmarkModel* model,
                          const bookmarks::BookmarkNode* parent,
                          int index) override;
   void BookmarkNodeRemoved(bookmarks::BookmarkModel* model,
                            const bookmarks::BookmarkNode* parent,
@@ skipping 96 matching lines @@
       scoped_observer_;
 
   base::WeakPtrFactory<OfflinePageModel> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(OfflinePageModel);
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_OFFLINE_PAGE_MODEL_H_