Split HistoryClient in two objects

components/history/core/browser/thumbnail_database.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_THUMBNAIL_DATABASE_H_
 #define COMPONENTS_HISTORY_CORE_BROWSER_THUMBNAIL_DATABASE_H_
 
 #include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "components/history/core/browser/history_types.h"
 #include "sql/connection.h"
 #include "sql/init_status.h"
 #include "sql/meta_table.h"
 #include "sql/statement.h"
 
 namespace base {
 class FilePath;
 class RefCountedMemory;
 class Time;
 }
 
 namespace history {
 
-class HistoryClient;
+class HistoryBackendClient;
 
 // This database interface is owned by the history backend and runs on the
 // history thread. It is a totally separate component from history partially
 // because we may want to move it to its own thread in the future. The
 // operations we will do on this database will be slow, but we can tolerate
 // higher latency (it's OK for thumbnails to come in slower than the rest
 // of the data). Moving this to a separate thread would not block potentially
 // higher priority history operations.
 class ThumbnailDatabase {
  public:
-  explicit ThumbnailDatabase(HistoryClient* history_client);
+  explicit ThumbnailDatabase(HistoryBackendClient* backend_client);
   ~ThumbnailDatabase();
 
   // Must be called after creation but before any other methods are called.
   // When not INIT_OK, no other functions should be called.
   sql::InitStatus Init(const base::FilePath& db_name);
 
   // Computes and records various metrics for the database. Should only be
   // called once and only upon successful Init.
   void ComputeDatabaseMetrics();
 
@@ skipping 217 matching lines @@
 
   // Adds support for bitmap usage tracking.
   bool UpgradeToVersion8();
 
   // Returns true if the |favicons| database is missing a column.
   bool IsFaviconDBStructureIncorrect();
 
   sql::Connection db_;
   sql::MetaTable meta_table_;
 
-  HistoryClient* history_client_;
+  HistoryBackendClient* backend_client_;
 };
 
 }  // namespace history
 
 #endif  // COMPONENTS_HISTORY_CORE_BROWSER_THUMBNAIL_DATABASE_H_