Remove unused constant history::kThumbnailsFilename.

components/history/core/browser/history_backend.h

 // Copyright (c) 2012 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_HISTORY_CORE_BROWSER_HISTORY_BACKEND_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_HISTORY_BACKEND_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 548 matching lines @@
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, HostRankIfAvailable);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, RecordTopHostsMetrics);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, GetCountsAndLastVisitForOrigins);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, UpdateVisitDuration);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, ExpireHistoryForTimes);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, DeleteFTSIndexDatabases);
   FRIEND_TEST_ALL_PREFIXES(ProfileSyncServiceTypedUrlTest,
                            ProcessUserChangeRemove);
   friend class ::TestingProfile;
 
-  // Computes the name of the specified database on disk.
-  base::FilePath GetThumbnailFileName() const;
-
   // Returns the name of the Favicons database. This is the new name
   // of the Thumbnails database.
   base::FilePath GetFaviconsFileName() const;
 
   class URLQuerier;
   friend class URLQuerier;
 
   // Does the work of Init.
   void InitImpl(const HistoryDatabaseParams& history_database_params);
 
@@ skipping 306 matching lines @@
 
   // List of observers
   base::ObserverList<HistoryBackendObserver> observers_;
 
   DISALLOW_COPY_AND_ASSIGN(HistoryBackend);
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_HISTORY_BACKEND_H_