[fsp] Improve performance for reading small chunks of data.

chrome/browser/chromeos/fileapi/mtp_file_system_backend_delegate.cc

 // Copyright 2014 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.
 
 #include "chrome/browser/chromeos/fileapi/mtp_file_system_backend_delegate.h"
 #include "chrome/browser/media_galleries/fileapi/device_media_async_file_util.h"
 #include "webkit/browser/blob/file_stream_reader.h"
 #include "webkit/browser/fileapi/file_stream_writer.h"
 #include "webkit/browser/fileapi/file_system_url.h"
 
@@ skipping 13 matching lines @@
     fileapi::FileSystemType type) {
   DCHECK_EQ(fileapi::kFileSystemTypeDeviceMediaAsFileStorage, type);
 
   return device_media_async_file_util_.get();
 }
 
 scoped_ptr<webkit_blob::FileStreamReader>
 MTPFileSystemBackendDelegate::CreateFileStreamReader(
     const fileapi::FileSystemURL& url,
     int64 offset,
+    int64 length,
     const base::Time& expected_modification_time,
     fileapi::FileSystemContext* context) {
   DCHECK_EQ(fileapi::kFileSystemTypeDeviceMediaAsFileStorage, url.type());
 
   return device_media_async_file_util_->GetFileStreamReader(
       url, offset, expected_modification_time, context);
 }
 
 scoped_ptr<fileapi::FileStreamWriter>
 MTPFileSystemBackendDelegate::CreateFileStreamWriter(
     const fileapi::FileSystemURL& url,
     int64 offset,
     fileapi::FileSystemContext* context) {
   DCHECK_EQ(fileapi::kFileSystemTypeDeviceMediaAsFileStorage, url.type());
 
   // TODO(kinaba): support writing.
   return scoped_ptr<fileapi::FileStreamWriter>();
 }
 
 }  // namespace chromeos