Sync FileSystem: Drop is_fetching_changes_ flag and completion_callback

chrome/browser/sync_file_system/drive_file_sync_service.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_FILE_SYSTEM_DRIVE_FILE_SYNC_SERVICE_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_FILE_SYNC_SERVICE_H_
 
 #include <deque>
 #include <map>
 #include <set>
@@ skipping 376 matching lines @@
 
   // True when Drive File Sync Service is registered for Drive notifications.
   bool push_notification_registered_;
   // True once the first drive notification is received with OK state.
   bool push_notification_enabled_;
   // Timer to trigger fetching changes for incremental sync.
   base::OneShotTimer<DriveFileSyncService> polling_timer_;
   // If polling_delay_seconds_ is negative (<0) the timer won't start.
   int64 polling_delay_seconds_;
 
-  // Is set to true while the service is fetching changes for incremental
-  // sync. Polling will be disabled while this is true.
-  bool is_fetching_changes_;
+  bool has_unfetched_remote_change_;
 
   ObserverList<Observer> service_observers_;
   ObserverList<FileStatusObserver> file_status_observers_;
 
   // Use WeakPtrFactory instead of SupportsWeakPtr to revoke the weak pointer
   // in |token_|.
   base::WeakPtrFactory<DriveFileSyncService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DriveFileSyncService);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_DRIVE_FILE_SYNC_SERVICE_H_