Split HistoryClient in two objects

components/history/core/browser/history_service.cc

 // 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.
 
 // The history system runs on a background thread so that potentially slow
 // database operations don't delay the browser. This backend processing is
 // represented by HistoryBackend. The HistoryService's job is to dispatch to
 // that thread.
 //
 // Main thread                       History thread
@@ skipping 14 matching lines @@
 #include "base/location.h"
 #include "base/memory/ref_counted.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/thread_task_runner_handle.h"
 #include "base/threading/thread.h"
 #include "base/time/time.h"
 #include "base/trace_event/trace_event.h"
 #include "components/history/core/browser/download_row.h"
 #include "components/history/core/browser/history_backend.h"
+#include "components/history/core/browser/history_backend_client.h"
 #include "components/history/core/browser/history_client.h"
 #include "components/history/core/browser/history_database_params.h"
 #include "components/history/core/browser/history_db_task.h"
 #include "components/history/core/browser/history_service_observer.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/history/core/browser/in_memory_database.h"
 #include "components/history/core/browser/in_memory_history_backend.h"
 #include "components/history/core/browser/keyword_search_term.h"
 #include "components/history/core/browser/visit_database.h"
 #include "components/history/core/browser/visit_delegate.h"
@@ skipping 825 matching lines @@
   options.timer_slack = base::TIMER_SLACK_MAXIMUM;
   if (!thread_->StartWithOptions(options)) {
     Cleanup();
     return false;
   }
 
   // Create the history backend.
   scoped_refptr<HistoryBackend> backend(new HistoryBackend(
       new BackendDelegate(weak_ptr_factory_.GetWeakPtr(),
                           base::ThreadTaskRunnerHandle::Get()),
-      history_client_.get(), thread_->task_runner()));
+      history_client_ ? history_client_->CreateBackendClient() : nullptr,
+      thread_->task_runner()));
   history_backend_.swap(backend);
 
   ScheduleTask(PRIORITY_UI,
                base::Bind(&HistoryBackend::Init, history_backend_.get(),
                           languages, no_db, history_database_params));
 
   if (visit_delegate_ && !visit_delegate_->Init(this))
     return false;
 
   return true;
@@ skipping 241 matching lines @@
   return favicon_changed_callback_list_.Add(callback);
 }
 
 void HistoryService::NotifyFaviconChanged(
     const std::set<GURL>& changed_favicons) {
   DCHECK(thread_checker_.CalledOnValidThread());
   favicon_changed_callback_list_.Notify(changed_favicons);
 }
 
 }  // namespace history