Add RequestOSFileHandle as a private PPAPI

ppapi/ppapi_sources.gypi

 # 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.
 
 {
   'variables': {
     'c_source_files': [
       'c/pp_array_output.h',
       'c/pp_bool.h',
       'c/pp_completion_callback.h',
@@ skipping 255 matching lines @@
       'cpp/dev/zoom_dev.cc',
       'cpp/dev/zoom_dev.h',
 
       # Deprecated interfaces.
       'cpp/dev/scriptable_object_deprecated.h',
       'cpp/dev/scriptable_object_deprecated.cc',
 
       # Private interfaces.
       'cpp/private/content_decryptor_private.cc',
       'cpp/private/content_decryptor_private.h',
+      'cpp/private/file_io_private.cc',
+      'cpp/private/file_io_private.h',
       'cpp/private/flash.cc',
       'cpp/private/flash.h',
       'cpp/private/flash_clipboard.cc',
       'cpp/private/flash_clipboard.h',
       'cpp/private/flash_device_id.cc',
       'cpp/private/flash_device_id.h',
       'cpp/private/flash_file.cc',
       'cpp/private/flash_file.h',
       'cpp/private/flash_font_file.cc',
       'cpp/private/flash_font_file.h',
@@ skipping 218 matching lines @@
       'tests/test_x509_certificate_private.h',
 
       # Deprecated test cases.
       'tests/test_instance_deprecated.cc',
       'tests/test_instance_deprecated.h',
       'tests/test_var_deprecated.cc',
       'tests/test_var_deprecated.h',
     ],
   },
 }