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

webkit/browser/fileapi/isolated_file_system_backend.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_BROWSER_FILEAPI_ISOLATED_FILE_SYSTEM_BACKEND_H_
 #define WEBKIT_BROWSER_FILEAPI_ISOLATED_FILE_SYSTEM_BACKEND_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "webkit/browser/fileapi/file_system_backend.h"
 
@@ skipping 19 matching lines @@
   virtual FileSystemOperation* CreateFileSystemOperation(
       const FileSystemURL& url,
       FileSystemContext* context,
       base::File::Error* error_code) const OVERRIDE;
   virtual bool SupportsStreaming(const FileSystemURL& url) const OVERRIDE;
   virtual bool HasInplaceCopyImplementation(
       fileapi::FileSystemType type) const OVERRIDE;
   virtual scoped_ptr<webkit_blob::FileStreamReader> CreateFileStreamReader(
       const FileSystemURL& url,
       int64 offset,
+      int64 length,
       const base::Time& expected_modification_time,
       FileSystemContext* context) const OVERRIDE;
   virtual scoped_ptr<FileStreamWriter> CreateFileStreamWriter(
       const FileSystemURL& url,
       int64 offset,
       FileSystemContext* context) const OVERRIDE;
   virtual FileSystemQuotaUtil* GetQuotaUtil() OVERRIDE;
 
  private:
   scoped_ptr<AsyncFileUtilAdapter> isolated_file_util_;
   scoped_ptr<AsyncFileUtilAdapter> dragged_file_util_;
   scoped_ptr<AsyncFileUtilAdapter> transient_file_util_;
 };
 
 }  // namespace fileapi
 
 #endif  // WEBKIT_BROWSER_FILEAPI_ISOLATED_FILE_SYSTEM_BACKEND_H_