Make largest_changestamp setter/getter asynchronous.

chrome/browser/chromeos/drive/mock_drive_file_system.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_MOCK_DRIVE_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_MOCK_DRIVE_FILE_SYSTEM_H_
 
 #include <string>
 
 #include "chrome/browser/chromeos/drive/drive_file_system_interface.h"
@@ skipping 79 matching lines @@
   MOCK_METHOD1(RequestDirectoryRefresh,
                void(const FilePath& file_path));
   MOCK_METHOD1(GetAvailableSpace,
                void(const GetAvailableSpaceCallback& callback));
   // This function is not mockable by gmock because scoped_ptr is not supported.
   virtual void AddUploadedFile(const FilePath& file,
                                scoped_ptr<google_apis::ResourceEntry> entry,
                                const FilePath& file_content_path,
                                const FileOperationCallback& callback) OVERRIDE {
   }
-  MOCK_CONST_METHOD0(GetMetadata, DriveFileSystemMetadata());
+  MOCK_METHOD1(GetMetadata,
+               void(const GetFilesystemMetadataCallback& callback));
   MOCK_METHOD0(Reload, void());
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_MOCK_DRIVE_FILE_SYSTEM_H_