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

webkit/browser/fileapi/file_system_context.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/file_system_context.h"
 
 #include "base/bind.h"
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/task_runner_util.h"
@@ skipping 405 matching lines @@
                  base::Unretained(quota_manager_proxy()),
                  origin_url,
                  type),
       callback);
 }
 
 scoped_ptr<webkit_blob::FileStreamReader>
 FileSystemContext::CreateFileStreamReader(
     const FileSystemURL& url,
     int64 offset,
+    int64 length,
     const base::Time& expected_modification_time) {
   if (!url.is_valid())
     return scoped_ptr<webkit_blob::FileStreamReader>();
   FileSystemBackend* backend = GetFileSystemBackend(url.type());
   if (!backend)
     return scoped_ptr<webkit_blob::FileStreamReader>();
   return backend->CreateFileStreamReader(
-      url, offset, expected_modification_time, this);
+      url, offset, length, expected_modification_time, this);
 }
 
 scoped_ptr<FileStreamWriter> FileSystemContext::CreateFileStreamWriter(
     const FileSystemURL& url,
     int64 offset) {
   if (!url.is_valid())
     return scoped_ptr<FileStreamWriter>();
   FileSystemBackend* backend = GetFileSystemBackend(url.type());
   if (!backend)
     return scoped_ptr<FileStreamWriter>();
@@ skipping 177 matching lines @@
   } else if (parent != child) {
     bool result = parent.AppendRelativePath(child, &path);
     DCHECK(result);
   }
 
   operation_runner()->GetMetadata(
       url, base::Bind(&DidGetMetadataForResolveURL, path, callback, info));
 }
 
 }  // namespace fileapi