Fix swarming tests not running in parallel

tools-webrtc/mb/mb_unittest.py

 #!/usr/bin/python
 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 """Tests for mb.py."""
@@ skipping 423 matching lines @@
                       '/fake_src/testing/buildbot/gn_isolate_map.pyl'],
                      files=test_files, ret=0)
 
     isolate_file = mbw.files['/fake_src/out/Default/base_unittests.isolate']
     isolate_file_contents = ast.literal_eval(isolate_file)
     files = isolate_file_contents['variables']['files']
     command = isolate_file_contents['variables']['command']
 
     self.assertEqual(files, [
         '../../testing/test_env.py',
+        '../../third_party/gtest-parallel/gtest-parallel',
+        '../../tools-webrtc/gtest-parallel-wrapper.py',
         'base_unittests',
     ])
     self.assertEqual(command, [
         '../../testing/test_env.py',
+        '../../tools-webrtc/gtest-parallel-wrapper.py',
+        '--output_dir=${ISOLATED_OUTDIR}/test_logs',
         './base_unittests',
+        '--workers=1',
         '--',
         '--asan=0',
         '--msan=0',
         '--tsan=0',
     ])
 
   def test_gn_isolate_windowed_test_launcher_linux(self):
     test_files = {
       '/tmp/swarming_targets': 'base_unittests\n',
       '/fake_src/testing/buildbot/gn_isolate_map.pyl': (
@@ skipping 303 matching lines @@
     self.check(['lookup', '-c', 'fake_config'], mbw=mbw,
                ret=0,
                out=("GYP_DEFINES='foo=bar baz=1'\n"
                     "GYP_LINK_CONCURRENCY=1\n"
                     "LLVM_FORCE_HEAD_REVISION=1\n"
                     "python build/gyp_chromium -G output_dir=_path_\n"))
 
 
 if __name__ == '__main__':
   unittest.main()