[fsp] Add support for truncating files.

chrome/chrome_tests_unit.gypi

 # Copyright 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.
 {
   'targets': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 733 matching lines @@
         'browser/chromeos/file_system_provider/operations/delete_entry_unittest.cc',
         'browser/chromeos/file_system_provider/operations/get_metadata_unittest.cc',
         'browser/chromeos/file_system_provider/operations/move_entry_unittest.cc',
         'browser/chromeos/file_system_provider/operations/open_file_unittest.cc',
         'browser/chromeos/file_system_provider/operations/read_directory_unittest.cc',
         'browser/chromeos/file_system_provider/operations/read_file_unittest.cc',
         'browser/chromeos/file_system_provider/operations/test_util.cc',
         'browser/chromeos/file_system_provider/operations/test_util.cc',
         'browser/chromeos/file_system_provider/operations/test_util.h',
         'browser/chromeos/file_system_provider/operations/test_util.h',
+        'browser/chromeos/file_system_provider/operations/truncate_unittest.cc',
         'browser/chromeos/file_system_provider/operations/unmount_unittest.cc',
         'browser/chromeos/file_system_provider/request_manager_unittest.cc',
         'browser/chromeos/file_system_provider/service_unittest.cc',
         'browser/chromeos/fileapi/file_access_permissions_unittest.cc',
         'browser/chromeos/fileapi/file_system_backend_unittest.cc',
         'browser/chromeos/geolocation/simple_geolocation_unittest.cc',
         'browser/chromeos/imageburner/burn_device_handler_unittest.cc',
         'browser/chromeos/imageburner/burn_manager_unittest.cc',
         'browser/chromeos/input_method/browser_state_monitor_unittest.cc',
         'browser/chromeos/input_method/input_method_configuration_unittest.cc',
@@ skipping 2158 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }