Don't allow multiple opens for Pepper FileSystem.

ppapi/ppapi_tests.gypi

 # Copyright (c) 2010 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.
 
 {
   'targets': [
      {
       'target_name': 'ppapi_example',
       'dependencies': [
         'ppapi_cpp'
@@ skipping 172 matching lines @@
         'tests/test_char_set.h',
         'tests/test_class.cc',
         'tests/test_class.h',
         'tests/test_cpp_includes.cc',
         'tests/test_directory_reader.cc',
         'tests/test_directory_reader.h',
         'tests/test_file_io.cc',
         'tests/test_file_io.h',
         'tests/test_file_ref.cc',
         'tests/test_file_ref.h',
+        'tests/test_file_system.cc',
+        'tests/test_file_system.h',
         'tests/test_graphics_2d.cc',
         'tests/test_graphics_2d.h',
         'tests/test_image_data.cc',
         'tests/test_image_data.h',
         'tests/test_paint_aggregator.cc',
         'tests/test_paint_aggregator.h',
         'tests/test_scrollbar.cc',
         'tests/test_scrollbar.h',
         'tests/test_struct_sizes.c',
         'tests/test_transport.cc',
@@ skipping 70 matching lines @@
         'proxy/plugin_dispatcher_unittest.cc',
         'proxy/plugin_resource_tracker_unittest.cc',
         'proxy/plugin_var_tracker_unittest.cc',
         'proxy/ppapi_proxy_test.cc',
         'proxy/ppapi_proxy_test.h',
         'proxy/serialized_var_unittest.cc',
       ],
     },
   ],
 }