drive: Remove polling code from DriveFileSystem

chrome/browser/chromeos/drive/drive_file_system_metadata.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_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_METADATA_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_METADATA_H_
 
 #include "base/basictypes.h"
 #include "base/time.h"
 #include "chrome/browser/chromeos/drive/drive_file_error.h"
@@ skipping 11 matching lines @@
 
   // True if the file system feed is loaded from the cache or from the server.
   bool loaded;
 
   // True if the feed is now being fetched from the server.
   bool refreshing;
 
   // True if push notification is enabled.
   bool push_notification_enabled;
 
-  // Polling interval time in seconds used for fetching delta feeds
-  // periodically.
-  int polling_interval_sec;
-
   // Time of the last update check.
   base::Time last_update_check_time;
 
   // Error code of the last update check.
   DriveFileError last_update_check_error;
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_METADATA_H_