Revert of Transform ImagePreReader into PreReadFile.

chrome/app/file_pre_reader_win.h

-// 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.
-
-// This file defines a function to pre-read a file in order to avoid touching
-// the disk when it is subsequently used.
-
-#ifndef CHROME_APP_FILE_PRE_READER_WIN_H_
-#define CHROME_APP_FILE_PRE_READER_WIN_H_
-
-namespace base {
-class FilePath;
-}
-
-// Reads |file_path| to avoid touching the disk when the file is actually used.
-// The function checks the Windows version to determine which pre-reading
-// mechanism to use. On Vista+, chunks of |step_size| bytes are read into a
-// buffer. The bigger |step_size| is, the faster the file is pre-read (up to
-// about 4MB according to local tests), but also the more memory is allocated
-// for the buffer.
-bool PreReadFile(const base::FilePath& file_path, int step_size);
-
-#endif  // CHROME_APP_FILE_PRE_READER_WIN_H_