Add cloud_print to the GN build.

cloud_print/cloud_print.gyp

 # 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,
   },
   'targets': [
     {
+      # GN version: //cloud_print
       'target_name': 'cloud_print',
       'type': 'none',
       'dependencies': [
         'gcp20/prototype/gcp20_device.gyp:*',
         'service/service.gyp:*',
       ],
       'conditions': [
         ['OS=="win"', {
           'dependencies': [
             'service/win/service.gyp:*',
             'virtual_driver/win/install/virtual_driver_install.gyp:*',
             'virtual_driver/win/virtual_driver.gyp:*',
           ],
         }],
         ['OS=="win" and target_arch=="ia32"', {
           'dependencies': [
             'virtual_driver/win/virtual_driver64.gyp:*',
           ],
         }],
       ],
     },
     {
+      # GN version: //cloud_print:cloud_print_unittests
       'target_name': 'cloud_print_unittests',
       'type': 'executable',
       'sources': [
         'service/service_state_unittest.cc',
       ],
       'dependencies': [
         '<(DEPTH)/base/base.gyp:base',
         '<(DEPTH)/base/base.gyp:run_all_unittests',
         '<(DEPTH)/base/base.gyp:test_support_base',
         '<(DEPTH)/testing/gmock.gyp:gmock',
@@ skipping 20 matching lines @@
       'msvs_settings': {
         'VCLinkerTool': {
           'AdditionalDependencies': [
               'secur32.lib',
           ],
         },
       },
     },
   ],
 }