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

chrome/browser/chromeos/fileapi/file_system_backend_delegate.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_CHROMEOS_FILEAPI_FILE_SYSTEM_BACKEND_DELEGATE_H_
 #define CHROME_BROWSER_CHROMEOS_FILEAPI_FILE_SYSTEM_BACKEND_DELEGATE_H_
 
 #include "base/basictypes.h"
 #include "base/callback_forward.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 24 matching lines @@
   virtual ~FileSystemBackendDelegate() {}
 
   // Called from FileSystemBackend::GetAsyncFileUtil().
   virtual storage::AsyncFileUtil* GetAsyncFileUtil(
       storage::FileSystemType type) = 0;
 
   // Called from FileSystemBackend::CreateFileStreamReader().
   virtual scoped_ptr<storage::FileStreamReader> CreateFileStreamReader(
       const storage::FileSystemURL& url,
       int64 offset,
+      int64 max_bytes_to_read,
       const base::Time& expected_modification_time,
       storage::FileSystemContext* context) = 0;
 
   // Called from FileSystemBackend::CreateFileStreamWriter().
   virtual scoped_ptr<storage::FileStreamWriter> CreateFileStreamWriter(
       const storage::FileSystemURL& url,
       int64 offset,
       storage::FileSystemContext* context) = 0;
 
   // Called from the FileSystemWatcherService class. The returned pointer must
   // stay valid until shutdown.
   virtual storage::WatcherManager* GetWatcherManager(
       const storage::FileSystemURL& url) = 0;
 
   // Called from FileSystemBackend::GetRedirectURLForContents.  Please ensure
   // that the returned URL is secure to be opened in a browser tab, or referred
   // from <img>, <video>, XMLHttpRequest, etc...
   virtual void GetRedirectURLForContents(
       const storage::FileSystemURL& url,
       const storage::URLCallback& callback) = 0;
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_FILEAPI_FILE_SYSTEM_BACKEND_DELEGATE_H_