Add cloud_print to the GN build.

cloud_print/virtual_driver/win/virtual_driver.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': {
     'chromium_code': 1,
    },
   'target_defaults': {
     'include_dirs': [
       '<(DEPTH)',
     ],
     'libraries': [
       'userenv.lib',
     ],
   },
   'targets' : [
     {
+      # GN version: //cloud_print/virtual_driver/win
       'target_name': 'virtual_driver_lib<(virtual_driver_suffix)',
       'type': 'static_library',
       'sources': [
         '<(DEPTH)/cloud_print/common/win/cloud_print_utils.cc',
         '<(DEPTH)/cloud_print/common/win/cloud_print_utils.h',
         'virtual_driver_consts.cc',
         'virtual_driver_consts.h',
         'virtual_driver_helpers.cc',
         'virtual_driver_helpers.h',
       ],
     },
     {
+      # GN version: //cloud_print/virtual_driver/win/port_monitor:lib
       'target_name': 'gcp_portmon_lib<(virtual_driver_suffix)',
       'type': 'static_library',
       'sources': [
         'port_monitor/port_monitor.cc',
         'port_monitor/port_monitor.h',
       ],
       'dependencies': [
         'virtual_driver_lib<(virtual_driver_suffix)',
       ],
     },
     {
+      # GN version: //cloud_print/virtual_driver/win/port_monitor
       'target_name': 'gcp_portmon<(virtual_driver_suffix)',
       'type': 'loadable_module',
       'sources': [
         'port_monitor/port_monitor.def',
         'port_monitor/port_monitor_dll.cc',
         '<(SHARED_INTERMEDIATE_DIR)/cloud_print/gcp_portmon<(virtual_driver_suffix)_dll_version.rc',
       ],
       'dependencies': [
         'gcp_portmon_lib<(virtual_driver_suffix)',
         '<(DEPTH)/chrome/chrome.gyp:chrome_version_header',
         '<(DEPTH)/cloud_print/cloud_print_resources.gyp:cloud_print_version_resources',
       ],
       'include_dirs': [
         # To allow including "version.h"
         '<(SHARED_INTERMEDIATE_DIR)',
       ],
     },
   ],
 }