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

chrome/browser/sync_file_system/local/sync_file_system_backend.h

 // Copyright 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_SYNC_FILE_SYSTEM_LOCAL_SYNC_FILE_SYSTEM_BACKEND_H_
 #define CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_SYNC_FILE_SYSTEM_BACKEND_H_
 
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sync_file_system/sync_callbacks.h"
 #include "chrome/browser/sync_file_system/sync_status_code.h"
@@ skipping 32 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;
 
   static SyncFileSystemBackend* GetBackend(
       const fileapi::FileSystemContext* context);
@@ skipping 46 matching lines @@
       fileapi::OpenFileSystemMode mode,
       const OpenFileSystemCallback& callback,
       SyncStatusCode status);
 
   DISALLOW_COPY_AND_ASSIGN(SyncFileSystemBackend);
 };
 
 }  // namespace sync_file_system
 
 #endif  // CHROME_BROWSER_SYNC_FILE_SYSTEM_LOCAL_SYNC_FILE_SYSTEM_BACKEND_H_