fix virtual_test_suites() for browser_test ports

Tools/Scripts/webkitpy/layout_tests/port/port_testcase.py

 # Copyright (C) 2010 Google 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.
 #    * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 21 matching lines @@
 import logging
 import os
 import socket
 import sys
 import time
 import unittest
 
 from webkitpy.common.system.executive_mock import MockExecutive, MockExecutive2
 from webkitpy.common.system.filesystem_mock import MockFileSystem
 from webkitpy.common.system.outputcapture import OutputCapture
+from webkitpy.common.system.systemhost import SystemHost
 from webkitpy.common.system.systemhost_mock import MockSystemHost
 from webkitpy.layout_tests.models import test_run_results
 from webkitpy.layout_tests.port.base import Port, TestConfiguration
 from webkitpy.layout_tests.port.server_process_mock import MockServerProcess
 from webkitpy.tool.mocktool import MockOptions
 
 
 # FIXME: get rid of this fixture
 class TestWebKitPort(Port):
     port_name = "testwebkitport"
@@ skipping 406 matching lines @@
         saved_environ = os.environ.copy()
         try:
             os.environ['WEBKIT_HTTP_SERVER_CONF_PATH'] = '/existing/httpd.conf'
             self.assertEqual(port.path_to_apache_config_file(), '/existing/httpd.conf')
         finally:
             os.environ = saved_environ.copy()
 
     def test_additional_platform_directory(self):
         port = self.make_port(options=MockOptions(additional_platform_directory=['/tmp/foo']))
         self.assertEqual(port.baseline_search_path()[0], '/tmp/foo')
+
+    def test_virtual_test_suites(self):
+        port = self.make_port(host=SystemHost())
+
+        # Test that this returns *something* and doesn't raise an exception.
+        self.assertNotEqual(port.virtual_test_suites(), None)