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

storage/browser/fileapi/copy_or_move_operation_delegate.cc

 // Copyright (c) 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.
 
 #include "storage/browser/fileapi/copy_or_move_operation_delegate.h"
 
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "net/base/io_buffer.h"
 #include "net/base/net_errors.h"
@@ skipping 800 matching lines @@
         file_system_context()->GetCopyOrMoveFileValidatorFactory(
             dest_root_.type(), &error);
     if (error != base::File::FILE_OK) {
       callback.Run(error);
       return;
     }
 
     if (!validator_factory) {
       scoped_ptr<storage::FileStreamReader> reader =
           file_system_context()->CreateFileStreamReader(
-              src_url, 0, base::Time());
+              src_url, 0 /* offset */, storage::kMaximumLength, base::Time());
       scoped_ptr<FileStreamWriter> writer =
           file_system_context()->CreateFileStreamWriter(dest_url, 0);
       if (reader && writer) {
         impl = new StreamCopyOrMoveImpl(
             operation_runner(),
             file_system_context(),
             operation_type_,
             src_url,
             dest_url,
             option_,
@@ skipping 193 matching lines @@
   base::FilePath relative = dest_root_.virtual_path();
   src_root_.virtual_path().AppendRelativePath(src_url.virtual_path(),
                                               &relative);
   return file_system_context()->CreateCrackedFileSystemURL(
       dest_root_.origin(),
       dest_root_.mount_type(),
       relative);
 }
 
 }  // namespace storage