Refactor multiprocess test code to allow multiple child processes to be launched.

test/test_test.gyp

 # Copyright 2015 The Crashpad Authors. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
 # You may obtain a copy of the License at
 #
 #     http://www.apache.org/licenses/LICENSE-2.0
 #
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 21 matching lines @@
       ],
       'include_dirs': [
         '..',
       ],
       'sources': [
         'mac/mach_multiprocess_test.cc',
         'multiprocess_exec_test.cc',
         'multiprocess_posix_test.cc',
         'paths_test.cc',
         'scoped_temp_dir_test.cc',
+        'win/win_child_process_test.cc',
         'win/win_multiprocess_test.cc',
       ],
     },
     {
       'target_name': 'crashpad_test_test_multiprocess_exec_test_child',
       'type': 'executable',
       'sources': [
         'multiprocess_exec_test_child.cc',
       ],
     },
   ],
 }