Rename OperationObserver to OperationDelegate

chrome/browser/chromeos/drive/file_system/operation_delegate.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_FILE_SYSTEM_OPERATION_OBSERVER_H_
-#define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_OPERATION_OBSERVER_H_
+#ifndef CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_OPERATION_DELEGATE_H_
+#define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_OPERATION_DELEGATE_H_
 
 #include "chrome/browser/chromeos/drive/file_errors.h"
 
 namespace base {
 class FilePath;
 }
 
 namespace drive {
 class FileChange;
 
 namespace file_system {
 
 // Error type of sync client.
 // Keep it synced with "DriveSyncErrorType" in file_manager_private.idl.
 enum DriveSyncErrorType {
   // Request to delete a file without permission.
   DRIVE_SYNC_ERROR_DELETE_WITHOUT_PERMISSION,
   // Google Drive is temporary unavailable.
   DRIVE_SYNC_ERROR_SERVICE_UNAVAILABLE,
   // Errors other than above ones. No fallback is provided for the error.
   DRIVE_SYNC_ERROR_MISC,
 };
 
 // Passes notifications from Drive operations back to the file system.
-// TODO(hashimoto): Give this class a more appropriate name.
-class OperationObserver {
+class OperationDelegate {
  public:
   // Sent when a content of a directory has been changed.
   // |directory_path| is a virtual directory path representing the
   // changed directory.
-  virtual void OnFileChangedByOperation(const FileChange& changed_files) = 0;
+  virtual void OnFileChangedByOperation(const FileChange& changed_files) {}
 
   // Sent when an entry is updated and sync is needed.
   virtual void OnEntryUpdatedByOperation(const std::string& local_id) {}
 
   // Sent when a specific drive sync error occurred.
   // |local_id| is the local ID of the resource entry.
   virtual void OnDriveSyncError(DriveSyncErrorType type,
                                 const std::string& local_id) {}
 
   // Waits for the sync task to complete and runs the callback.
   // Returns false if no task is found for the spcecified ID.
   virtual bool WaitForSyncComplete(const std::string& local_id,
                                    const FileOperationCallback& callback);
 };
 
 }  // namespace file_system
 }  // namespace drive
 
-#endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_OPERATION_OBSERVER_H_
+#endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_OPERATION_DELEGATE_H_