Convert sandbox_mac_unittests to run exclusively on Swarming

sandbox/mac/sandbox_mac.gypi

 # Copyright 2014 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': 'sandbox',
       'type': '<(component)',
       'sources': [
@@ skipping 93 matching lines @@
         '..',
       ],
       'link_settings': {
         'libraries': [
           '$(SDKROOT)/System/Library/Frameworks/CoreFoundation.framework',
           '$(SDKROOT)/System/Library/Frameworks/Foundation.framework',
         ],
       },
     },
   ],
+  'conditions': [
+    ['test_isolation_mode != "noop"', {
+      'targets': [
+        {
+          'target_name': 'sandbox_mac_unittests_run',
+          'type': 'none',
+          'dependencies': [
+            'sandbox_mac_unittests',
+          ],
+          'includes': [ '../../build/isolate.gypi' ],
+          'sources': [ '../sandbox_mac_unittests.isolate' ],
+        },
+      ],
+    }],
+  ],
 }