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

chrome/browser/media_galleries/fileapi/media_file_system_backend.h

 // Copyright (c) 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_MEDIA_GALLERIES_FILEAPI_MEDIA_FILE_SYSTEM_BACKEND_H_
 #define CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MEDIA_FILE_SYSTEM_BACKEND_H_
 
 #include <string>
 
 #include "base/callback.h"
@@ skipping 58 matching lines @@
       const fileapi::FileSystemURL& url,
       fileapi::FileSystemContext* context,
       base::File::Error* error_code) const OVERRIDE;
   virtual bool SupportsStreaming(
       const fileapi::FileSystemURL& url) const OVERRIDE;
   virtual bool HasInplaceCopyImplementation(
       fileapi::FileSystemType type) const OVERRIDE;
   virtual scoped_ptr<webkit_blob::FileStreamReader> CreateFileStreamReader(
       const fileapi::FileSystemURL& url,
       int64 offset,
+      int64 length,
       const base::Time& expected_modification_time,
       fileapi::FileSystemContext* context) const OVERRIDE;
   virtual scoped_ptr<fileapi::FileStreamWriter> CreateFileStreamWriter(
       const fileapi::FileSystemURL& url,
       int64 offset,
       fileapi::FileSystemContext* context) const OVERRIDE;
   virtual fileapi::FileSystemQuotaUtil* GetQuotaUtil() OVERRIDE;
 
  private:
   // Store the profile path. We need this to create temporary snapshot files.
@@ skipping 12 matching lines @@
   scoped_ptr<fileapi::AsyncFileUtil> itunes_file_util_;
 #endif  // defined(OS_WIN) || defined(OS_MACOSX)
 #if defined(OS_MACOSX)
   scoped_ptr<fileapi::AsyncFileUtil> iphoto_file_util_;
 #endif  // defined(OS_MACOSX)
 
   DISALLOW_COPY_AND_ASSIGN(MediaFileSystemBackend);
 };
 
 #endif  // CHROME_BROWSER_MEDIA_GALLERIES_FILEAPI_MEDIA_FILE_SYSTEM_BACKEND_H_