Implement TouchFile on drive::FileSystem.

chrome/chrome_browser_chromeos.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.
 
 {
   'targets': [
     {
       'target_name': 'browser_chromeos',
       'type': 'static_library',
@@ skipping 234 matching lines @@
         'browser/chromeos/drive/file_system/create_file_operation.h',
         'browser/chromeos/drive/file_system/drive_operations.cc',
         'browser/chromeos/drive/file_system/drive_operations.h',
         'browser/chromeos/drive/file_system/move_operation.cc',
         'browser/chromeos/drive/file_system/move_operation.h',
         'browser/chromeos/drive/file_system/operation_observer.h',
         'browser/chromeos/drive/file_system/remove_operation.cc',
         'browser/chromeos/drive/file_system/remove_operation.h',
         'browser/chromeos/drive/file_system/search_operation.cc',
         'browser/chromeos/drive/file_system/search_operation.h',
+        'browser/chromeos/drive/file_system/touch_operation.cc',
+        'browser/chromeos/drive/file_system/touch_operation.h',
         'browser/chromeos/drive/file_system/update_operation.cc',
         'browser/chromeos/drive/file_system/update_operation.h',
         'browser/chromeos/drive/file_system_interface.h',
         'browser/chromeos/drive/file_system_metadata.cc',
         'browser/chromeos/drive/file_system_metadata.h',
         'browser/chromeos/drive/file_system_observer.h',
         'browser/chromeos/drive/file_system_proxy.cc',
         'browser/chromeos/drive/file_system_proxy.h',
         'browser/chromeos/drive/file_system_util.cc',
         'browser/chromeos/drive/file_system_util.h',
@@ skipping 650 matching lines @@
         'browser/chromeos/attestation/attestation_key_payload.proto',
       ],
       'variables': {
         'proto_in_dir': 'browser/chromeos/attestation',
         'proto_out_dir': 'chrome/browser/chromeos/attestation',
       },
       'includes': [ '../build/protoc.gypi' ]
     },
   ],
 }