Add SystemSnapshotMac and its test

snapshot/snapshot.gyp

 # Copyright 2014 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 16 matching lines @@
       ],
       'sources': [
         'cpu_architecture.h',
         'cpu_context.cc',
         'cpu_context.h',
         'exception_snapshot.h',
         'memory_snapshot.h',
         'module_snapshot.h',
         'process_snapshot.h',
         'system_snapshot.h',
+        'system_snapshot_mac.cc',
+        'system_snapshot_mac.h',
         'thread_snapshot.h',
       ],
     },
+    {
+      'target_name': 'snapshot_test',
+      'type': 'executable',
+      'dependencies': [
+        'snapshot',
+        '../compat/compat.gyp:compat',
+        '../third_party/gtest/gtest.gyp:gtest',
+        '../third_party/gtest/gtest.gyp:gtest_main',
+        '../third_party/mini_chromium/mini_chromium/base/base.gyp:base',
+        '../util/util.gyp:util',
+        '../util/util.gyp:util_test_lib',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+      'sources': [
+        'system_snapshot_mac_test.cc',
+      ],
+    },
   ],
 }