Flush at the end of local file writing in FileWriter API.

webkit/fileapi/file_stream_writer.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 WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_
 #define WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_
 
 #include "base/basictypes.h"
 #include "net/base/completion_callback.h"
 #include "webkit/fileapi/fileapi_export.h"
@@ skipping 37 matching lines @@
   // cancel could not be performed, it returns an error code. Especially when
   // there is no in-flight operation, net::ERR_UNEXPECTED is returned.
   // Otherwise, net::ERR_IO_PENDING is returned, and the callback will be run on
   // the thread where Cancel() was called when the cancel has completed. It is
   // invalid to call Cancel() more than once on the same async operation.
   //
   // In either case, the callback function passed to the in-flight async
   // operation is dismissed immediately when Cancel() is called, and thus
   // will never be called.
   virtual int Cancel(const net::CompletionCallback& callback) = 0;
+
+  // Flushes the data written so far.
+  virtual int Flush(const net::CompletionCallback& callback) = 0;
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_FILEAPI_FILE_STREAM_WRITER_H_