Convert sync_unit_tests to run exclusively on Swarming

sync/sync_tests.gypi

 # Copyright 2013 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': [
     # Test support files for the 'sync_core' target.
     # GN version: //sync:test_support_sync_core
     {
       'target_name': 'test_support_sync_core',
@@ skipping 489 matching lines @@
             'sync_unit_tests',
           ],
           'variables': {
             'test_suite_name': 'sync_unit_tests',
             'isolate_file': 'sync_unit_tests.isolate',
           },
           'includes': [ '../build/apk_test.gypi' ],
         },
       ],
     }],
+    ['test_isolation_mode != "noop"', {
+      'targets': [
+        {
+          'target_name': 'sync_unit_tests_run',
+          'type': 'none',
+          'dependencies': [
+            'sync_unit_tests',
+          ],
+          'includes': [
+            '../build/isolate.gypi',
+          ],
+          'sources': [
+            'sync_unit_tests.isolate',
+          ],
+        },
+      ],
+    }],
   ],
 }