Add an additional content_shell per worker for running virtual tests.

Tools/Scripts/webkitpy/layout_tests/run_webkit_tests_unittest.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
 # Copyright (C) 2010 Gabor Rapcsanyi (rgabor@inf.u-szeged.hu), University of Szeged
 # Copyright (C) 2011 Apple Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
@@ skipping 759 matching lines @@
         self.assertEqual(results["num_flaky"], 0)
 
     def test_reftest_crash(self):
         test_results = get_test_results(['failures/unexpected/crash-reftest.html'])
         # The list of references should be empty since the test crashed and we didn't run any references.
         self.assertEqual(test_results[0].references, [])
 
     def test_reftest_with_virtual_reference(self):
         _, err, _ = logging_run(['--details', 'virtual/virtual_passes/passes/reftest.html'], tests_included=True)
         self.assertTrue('ref: virtual/virtual_passes/passes/reftest-expected.html' in err.getvalue())
+        self.assertTrue(
+            re.search('args: --virtual-arg\s*reference_args: --virtual-arg\s*ref:', err.getvalue()))
+
+    def test_reftest_virtual_references_use_default_args(self):
+        test_name = 'virtual/references_use_default_args/passes/reftest.html'
+        run_details, err, _ = logging_run(['--details', test_name], tests_included=True)
+        self.assertEqual(run_details.exit_code, 0)
+        self.assertEqual(run_details.initial_results.total, 1)
+        test_result = run_details.initial_results.all_results[0]
+        self.assertEqual(test_result.test_name, test_name)
+        self.assertEqual(test_result.references[0], 'passes/reftest-expected.html')
+        # reference_args should be empty since we are using the default flags.
+        self.assertTrue(re.search('reference_args:\s*ref:', err.getvalue()))
 
     def test_additional_platform_directory(self):
         self.assertTrue(passing_run(['--additional-platform-directory', '/tmp/foo']))
         self.assertTrue(passing_run(['--additional-platform-directory', '/tmp/../foo']))
         self.assertTrue(passing_run(['--additional-platform-directory', '/tmp/foo', '--additional-platform-directory', '/tmp/bar']))
         self.assertTrue(passing_run(['--additional-platform-directory', 'foo']))
 
     def test_additional_expectations(self):
         host = MockHost()
         host.filesystem.write_text_file('/tmp/overrides.txt', 'Bug(x) failures/unexpected/mismatch.html [ ImageOnlyFailure ]\n')
@@ skipping 261 matching lines @@
         stderr = StringIO.StringIO()
         res = run_webkit_tests.main(['--platform', 'test', '--exit-after-n-failures', '1',
                                      'failures/unexpected/missing_text.html',
                                      'failures/unexpected/missing_image.html'],
                                     stdout, stderr)
         self.assertEqual(res, test_run_results.EARLY_EXIT_STATUS)
         self.assertEqual(stdout.getvalue(),
                 ('\n'
                  'Regressions: Unexpected missing results (1)\n'
                  '  failures/unexpected/missing_image.html [ Missing ]\n\n'))