drive: Introduce DriveSystemServiceObserver

chrome/browser/chromeos/drive/drive_file_system_observer.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_OBSERVER_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_OBSERVER_H_
 
 #include "chrome/browser/chromeos/drive/drive_file_error.h"
 
 namespace base {
@@ skipping 14 matching lines @@
   }
 
   // Triggered when the file system is initially loaded.
   virtual void OnInitialLoadFinished() {
   }
 
   // Triggered when the feed from the server is loaded.
   virtual void OnFeedFromServerLoaded() {
   }
 
-  // Triggered when the file system is mounted.
-  virtual void OnFileSystemMounted() {
-  }
-
-  // Triggered when the file system is being unmounted.
-  virtual void OnFileSystemBeingUnmounted() {
-  }
-
  protected:
   virtual ~DriveFileSystemObserver() {}
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_OBSERVER_H_