Eliminate NOTIFICATION_HISTORY_LOADED notification

chrome/browser/sync/glue/bookmark_data_type_controller.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 CHROME_BROWSER_SYNC_GLUE_BOOKMARK_DATA_TYPE_CONTROLLER_H__
 #define CHROME_BROWSER_SYNC_GLUE_BOOKMARK_DATA_TYPE_CONTROLLER_H__
 
 #include <string>
 
 #include "base/compiler_specific.h"
+#include "base/scoped_observer.h"
 #include "chrome/browser/sync/glue/frontend_data_type_controller.h"
 #include "components/bookmarks/browser/base_bookmark_model_observer.h"
+#include "components/history/core/browser/history_service_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 
 namespace browser_sync {
 
 // A class that manages the startup and shutdown of bookmark sync.
 class BookmarkDataTypeController : public FrontendDataTypeController,
                                    public content::NotificationObserver,
-                                   public BaseBookmarkModelObserver {
+                                   public BaseBookmarkModelObserver,
+                                   public history::HistoryServiceObserver {
  public:
   BookmarkDataTypeController(ProfileSyncComponentsFactory* profile_sync_factory,
                              Profile* profile,
                              ProfileSyncService* sync_service);
 
   // FrontendDataTypeController interface.
   syncer::ModelType type() const override;
 
   // content::NotificationObserver interface.
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
+  // history::HistoryServiceObserver:
+  void OnHistoryServiceLoaded(HistoryService* service) override;
+
  private:
   ~BookmarkDataTypeController() override;
 
   // FrontendDataTypeController interface.
   bool StartModels() override;
   void CleanUpState() override;
   void CreateSyncComponents() override;
 
   // BaseBookmarkModelObserver interface.
   void BookmarkModelChanged() override;
   void BookmarkModelLoaded(BookmarkModel* model, bool ids_reassigned) override;
   void BookmarkModelBeingDeleted(BookmarkModel* model) override;
 
   // Helper that returns true iff both the bookmark model and the history
   // service have finished loading.
   bool DependentsLoaded();
 
-  content::NotificationRegistrar registrar_;
+  content::NotificationRegistrar notification_registrar_;
 
   BookmarkModel* bookmark_model_;
 
-  // Have we installed ourselves as a BookmarkModel observer?
-  bool installed_bookmark_observer_;
+  ScopedObserver<HistoryService, HistoryServiceObserver>
+      history_service_observer_;
+  ScopedObserver<BookmarkModel, BaseBookmarkModelObserver>
+      bookmark_model_observer_;
 
   DISALLOW_COPY_AND_ASSIGN(BookmarkDataTypeController);
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_GLUE_BOOKMARK_DATA_TYPE_CONTROLLER_H__