drive: Return cancel closure from FileSystem::GetFileContent

chrome/browser/chromeos/drive/dummy_file_system.h

 // Copyright 2013 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_DUMMY_FILE_SYSTEM_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_DUMMY_FILE_SYSTEM_H_
 
 #include "chrome/browser/chromeos/drive/file_system_interface.h"
 
 namespace drive {
@@ skipping 40 matching lines @@
                             int64 length,
                             const FileOperationCallback& callback) OVERRIDE {}
   virtual void Pin(const base::FilePath& file_path,
                    const FileOperationCallback& callback) OVERRIDE {}
   virtual void Unpin(const base::FilePath& file_path,
                      const FileOperationCallback& callback) OVERRIDE {}
   virtual void GetFile(const base::FilePath& file_path,
                        const GetFileCallback& callback) OVERRIDE {}
   virtual void GetFileForSaving(const base::FilePath& file_path,
                                 const GetFileCallback& callback) OVERRIDE {}
-  virtual void GetFileContent(
+  virtual base::Closure GetFileContent(
       const base::FilePath& file_path,
       const GetFileContentInitializedCallback& initialized_callback,
       const google_apis::GetContentCallback& get_content_callback,
-      const FileOperationCallback& completion_callback) OVERRIDE {}
+      const FileOperationCallback& completion_callback) OVERRIDE;
   virtual void GetResourceEntry(
       const base::FilePath& file_path,
       const GetResourceEntryCallback& callback) OVERRIDE {}
   virtual void ReadDirectory(const base::FilePath& file_path,
                              const ReadDirectoryCallback& callback) OVERRIDE {}
   virtual void Search(const std::string& search_query,
                       const GURL& next_link,
                       const SearchCallback& callback) OVERRIDE {}
   virtual void SearchMetadata(
       const std::string& query,
@@ skipping 21 matching lines @@
                              const FileOperationCallback& callback) OVERRIDE {}
   virtual void Reset(const FileOperationCallback& callback) OVERRIDE {}
   virtual void GetPathFromResourceId(const std::string& resource_id,
                                      const GetFilePathCallback& callback)
       OVERRIDE {}
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_DUMMY_FILE_SYSTEM_H_