Make largest_changestamp setter/getter asynchronous.

chrome/browser/chromeos/drive/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_DRIVE_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 116 matching lines @@
       const FilePath& directory_path,
       const ReadDirectoryWithSettingCallback& callback) OVERRIDE;
   virtual void RequestDirectoryRefresh(
       const FilePath& directory_path) OVERRIDE;
   virtual void GetAvailableSpace(
       const GetAvailableSpaceCallback& callback) OVERRIDE;
   virtual void AddUploadedFile(const FilePath& directory_path,
                                scoped_ptr<google_apis::ResourceEntry> doc_entry,
                                const FilePath& file_content_path,
                                const FileOperationCallback& callback) OVERRIDE;
-  virtual DriveFileSystemMetadata GetMetadata() const OVERRIDE;
+  virtual void GetMetadata(
+      const GetFilesystemMetadataCallback& callback) OVERRIDE;
   virtual void Reload() OVERRIDE;
 
   // file_system::OperationObserver overrides.
   virtual void OnDirectoryChangedByOperation(
       const FilePath& directory_path) OVERRIDE;
 
   // DriveFeedLoader::Observer overrides.
   // Used to propagate events from DriveFeedLoader.
   virtual void OnDirectoryChanged(const FilePath& directory_path) OVERRIDE;
   virtual void OnResourceListFetched(int num_accumulated_entries) OVERRIDE;
@@ skipping 519 matching lines @@
   // invalidate the weak pointers before any other members are destroyed.
   base::WeakPtrFactory<DriveFileSystem> ui_weak_ptr_factory_;
   // Unlike other classes, we need this as we need this to redirect a task
   // from IO thread to UI thread.
   base::WeakPtr<DriveFileSystem> ui_weak_ptr_;
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DRIVE_FILE_SYSTEM_H_