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

webkit/browser/fileapi/isolated_file_system_backend.cc

 // 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.
 
 #include "webkit/browser/fileapi/isolated_file_system_backend.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
@@ skipping 98 matching lines @@
     storage::FileSystemType type) const {
   DCHECK(type == kFileSystemTypeNativeLocal || type == kFileSystemTypeDragged ||
          type == kFileSystemTypeForTransientFile);
   return false;
 }
 
 scoped_ptr<storage::FileStreamReader>
 IsolatedFileSystemBackend::CreateFileStreamReader(
     const FileSystemURL& url,
     int64 offset,
+    int64 length,
     const base::Time& expected_modification_time,
     FileSystemContext* context) const {
   return scoped_ptr<storage::FileStreamReader>(
       storage::FileStreamReader::CreateForLocalFile(
           context->default_file_task_runner(),
           url.path(),
           offset,
           expected_modification_time));
 }
 
 scoped_ptr<FileStreamWriter> IsolatedFileSystemBackend::CreateFileStreamWriter(
     const FileSystemURL& url,
     int64 offset,
     FileSystemContext* context) const {
   return scoped_ptr<FileStreamWriter>(
       FileStreamWriter::CreateForLocalFile(
           context->default_file_task_runner(),
           url.path(),
           offset,
           FileStreamWriter::OPEN_EXISTING_FILE));
 }
 
 FileSystemQuotaUtil* IsolatedFileSystemBackend::GetQuotaUtil() {
   // No quota support.
   return NULL;
 }
 
 }  // namespace storage