Split HistoryClient in two objects

components/history/core/browser/BUILD.gn

 # 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.
 
 static_library("browser") {
   sources = [
     "delete_directive_handler.cc",
     "delete_directive_handler.h",
     "download_constants.h",
     "download_database.cc",
     "download_database.h",
     "download_row.cc",
     "download_row.h",
     "download_types.cc",
     "download_types.h",
     "expire_history_backend.cc",
     "expire_history_backend.h",
     "history_backend.cc",
     "history_backend.h",
+    "history_backend_client.h",
     "history_backend_notifier.h",
     "history_backend_observer.h",
-    "history_client.cc",
     "history_client.h",
     "history_constants.cc",
     "history_constants.h",
     "history_context.h",
     "history_database.cc",
     "history_database.h",
     "history_database_params.cc",
     "history_database_params.h",
     "history_db_task.h",
     "history_match.cc",
@@ skipping 87 matching lines @@
       "android/sql_handler.h",
       "android/urls_sql_handler.cc",
       "android/urls_sql_handler.h",
       "android/visit_sql_handler.cc",
       "android/visit_sql_handler.h",
     ]
   }
 
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 }