[fsp] Buffer consecutive Write() calls.

storage/browser/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 STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
 #define STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_
 
 #include "base/basictypes.h"
 #include "net/base/completion_callback.h"
 #include "storage/browser/storage_browser_export.h"
@@ skipping 28 matching lines @@
 
   // Writes to the current cursor position asynchronously.
   //
   // Up to buf_len bytes will be written.  (In other words, partial
   // writes are allowed.) If the write completed synchronously, it returns
   // the number of bytes written. If the operation could not be performed, it
   // returns an error code. Otherwise, net::ERR_IO_PENDING is returned, and the
   // callback will be run on the thread where Write() was called when the write
   // has completed.
   //
+  // After the last write, Flush() must be called unless the flushing on
+  // completion is explicitly disabled for the file system type, the writer is
+  // created for. See FileSystemContext::ShouldFlushOnWriteCompletion().
+  //
   // This errors out (either synchronously or via callback) with:
   //   net::ERR_FILE_NOT_FOUND: When the target file is not found.
   //   net::ERR_ACCESS_DENIED: When the target file is a directory or
   //      the writer has no permission on the file.
   //   net::ERR_FILE_NO_SPACE: When the write will result in out of quota
   //      or there is not enough room left on the disk.
   //
   // It is invalid to call Write while there is an in-flight async operation.
   virtual int Write(net::IOBuffer* buf, int buf_len,
                     const net::CompletionCallback& callback) = 0;
@@ skipping 19 matching lines @@
   // is returned, and the callback will be run on the thread where Flush() was
   // called when the flush has completed.
   //
   // It is invalid to call Flush while there is an in-flight async operation.
   virtual int Flush(const net::CompletionCallback& callback) = 0;
 };
 
 }  // namespace storage
 
 #endif  // STORAGE_BROWSER_FILEAPI_FILE_STREAM_WRITER_H_