Implement local storage for App List in case app sync is off.

chrome/browser/ui/app_list/app_list_syncable_service.h

 // Copyright 2013 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_UI_APP_LIST_APP_LIST_SYNCABLE_SERVICE_H_
 #define CHROME_BROWSER_UI_APP_LIST_APP_LIST_SYNCABLE_SERVICE_H_
 
 #include <stddef.h>
 
 #include <map>
@@ skipping 109 matching lines @@
 
   Profile* profile() { return profile_; }
   size_t GetNumSyncItemsForTest();
   const std::string& GetOemFolderNameForTest() const {
     return oem_folder_name_;
   }
   void ResetDriveAppProviderForTest();
 
   const SyncItemMap& sync_items() const { return sync_items_; }
 
+  // Returns true if sync is currently active.
+  bool is_active() const { return sync_processor_ != nullptr; }
+
   // syncer::SyncableService
   syncer::SyncMergeResult MergeDataAndStartSyncing(
       syncer::ModelType type,
       const syncer::SyncDataList& initial_sync_data,
       std::unique_ptr<syncer::SyncChangeProcessor> sync_processor,
       std::unique_ptr<syncer::SyncErrorFactory> error_handler) override;
   void StopSyncing(syncer::ModelType type) override;
   syncer::SyncDataList GetAllSyncData(syncer::ModelType type) const override;
   syncer::SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
@@ skipping 115 matching lines @@
 
   // Provides integration with Drive apps.
   std::unique_ptr<DriveAppProvider> drive_app_provider_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListSyncableService);
 };
 
 }  // namespace app_list
 
 #endif  // CHROME_BROWSER_UI_APP_LIST_APP_LIST_SYNCABLE_SERVICE_H_