drive: Return cancel closure from FileSystem::GetFileContent

chrome/browser/chromeos/drive/file_system_interface.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_INTERFACE_H_
 #define CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_INTERFACE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 53 matching lines @@
                             scoped_ptr<ResourceEntry> entry)>
     GetResourceEntryCallback;
 
 // Used to get files from the file system.
 typedef base::Callback<void(FileError error,
                             const base::FilePath& file_path,
                             scoped_ptr<ResourceEntry> entry)> GetFileCallback;
 
 // Used to get file content from the file system.
 // If the file content is available in local cache, |local_file| is filled with
-// the path to the cache file and |cancel_download_closure| is null. If the file
-// content starts to be downloaded from the server, |local_file| is empty and
-// |cancel_download_closure| is filled with a closure by calling which the
-// download job can be cancelled.
-// |cancel_download_closure| must be called on the UI thread.
+// the path to the cache file. If the file content starts to be downloaded from
+// the server, |local_file| is empty.
 typedef base::Callback<void(FileError error,
-                            scoped_ptr<ResourceEntry> entry,
                             const base::FilePath& local_file,
-                            const base::Closure& cancel_download_closure)>
+                            scoped_ptr<ResourceEntry> entry)>

[hashimoto, 2014/03/27 08:27:48]

|entry| and |local_file| are swapped to use the existing version of
google_apis::CreateRelayCallback.

     GetFileContentInitializedCallback;
 
 // Used to get list of entries under a directory.
 // If |error| is not FILE_ERROR_OK, |entries| is null.
 typedef base::Callback<void(FileError error,
                             scoped_ptr<ResourceEntryVector> entries,
                             bool has_more)>
     ReadDirectoryCallback;
 
 // Used to get drive content search results.
@@ skipping 236 matching lines @@
 
   // Makes sure that |file_path| in the file system is available in the local
   // cache, and mark it as dirty. The next modification to the cache file is
   // watched and is automatically uploaded to the server. If the entry is not
   // present in the file system, it is created.
   //
   // Returns the cache path and entry info to |callback|. It must not be null.
   virtual void GetFileForSaving(const base::FilePath& file_path,
                                 const GetFileCallback& callback) = 0;
 
-  // Gets a file by the given |file_path|.
+  // Gets a file by the given |file_path| and returns a closure to cancel the
+  // task.
   // Calls |initialized_callback| when either:
   //   1) The cached file (or JSON file for hosted file) is found, or
   //   2) Starting to download the file from drive server.
   // In case of 2), the given FilePath is empty, and |get_content_callback| is
   // called repeatedly with downloaded content following the
   // |initialized_callback| invocation.
   // |completion_callback| is invoked if an error is found, or the operation
   // is successfully done.
   // |initialized_callback|, |get_content_callback| and |completion_callback|
   // must not be null.
-  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) = 0;
 
   // Finds an entry (a file or a directory) by |file_path|. This call will also
   // retrieve and refresh file system content from server and disk cache.
   //
   // |callback| must not be null.
   virtual void GetResourceEntry(const base::FilePath& file_path,
@@ skipping 77 matching lines @@
   virtual void Reset(const FileOperationCallback& callback) = 0;
 
   // Finds a path of an entry (a file or a directory) by |resource_id|.
   virtual void GetPathFromResourceId(const std::string& resource_id,
                                      const GetFilePathCallback& callback) = 0;
 };
 
 }  // namespace drive
 
 #endif  // CHROME_BROWSER_CHROMEOS_DRIVE_FILE_SYSTEM_INTERFACE_H_