Remove unused ThumbnailDatabase::UpdateIconMapping() and ThumbnailDatabase::CloneIconMappings()

components/history/core/browser/history_backend.h

Index: components/history/core/browser/history_backend.h
diff --git a/components/history/core/browser/history_backend.h b/components/history/core/browser/history_backend.h
index 6c54b459df8f204bc306b8455854d991d31e80f3..9a58cd4c06076c33d6f4276eea67088d869200b5 100644
--- a/components/history/core/browser/history_backend.h
+++ b/components/history/core/browser/history_backend.h
@@ -300,8 +300,6 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
 
   void SetFaviconsOutOfDateForPage(const GURL& page_url);
 
-  void CloneFavicons(const GURL& old_page_url, const GURL& new_page_url);
-
   void SetImportedFavicons(
       const favicon_base::FaviconUsageDataList& favicon_usage);
 
@@ -505,8 +503,6 @@ class HistoryBackend : public base::RefCountedThreadSafe<HistoryBackend>,
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, GetFaviconsFromDBExpired);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest,
                            UpdateFaviconMappingsAndFetchNoDB);
-  FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest,
-                           CloneFaviconIsRestrictedToSameDomain);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, QueryFilteredURLs);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, UpdateVisitDuration);
   FRIEND_TEST_ALL_PREFIXES(HistoryBackendTest, ExpireHistoryForTimes);