Split HistoryClient in two objects

components/history.gypi

 # Copyright 2014 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.
 
 {
   'targets': [
     {
       # GN version: //components/history/core/browser
       'target_name': 'history_core_browser',
       'type': 'static_library',
@@ skipping 30 matching lines @@
         'history/core/browser/download_database.cc',
         'history/core/browser/download_database.h',
         'history/core/browser/download_row.cc',
         'history/core/browser/download_row.h',
         'history/core/browser/download_types.cc',
         'history/core/browser/download_types.h',
         'history/core/browser/expire_history_backend.cc',
         'history/core/browser/expire_history_backend.h',
         'history/core/browser/history_backend.cc',
         'history/core/browser/history_backend.h',
+        'history/core/browser/history_backend_client.h',
         'history/core/browser/history_backend_notifier.h',
         'history/core/browser/history_backend_observer.h',
-        'history/core/browser/history_client.cc',
         'history/core/browser/history_client.h',
         'history/core/browser/history_constants.cc',
         'history/core/browser/history_constants.h',
         'history/core/browser/history_context.h',
         'history/core/browser/history_database.cc',
         'history/core/browser/history_database.h',
         'history/core/browser/history_database_params.cc',
         'history/core/browser/history_database_params.h',
         'history/core/browser/history_db_task.h',
         'history/core/browser/history_match.cc',
@@ skipping 182 matching lines @@
             'history/ios/browser/history_database_helper.cc',
             'history/ios/browser/history_database_helper.h',
             'history/ios/browser/web_state_top_sites_observer.cc',
             'history/ios/browser/web_state_top_sites_observer.h',
           ],
         },
       ],
     }],
   ],
 }