Convert the last policy.PolicyTest pyauto test to a browser_test.

chrome/chrome_tests.gypi

 # Copyright (c) 2012 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.
 {
   'variables' : {
     'pyautolib_sources': [
       'app/chrome_command_ids.h',
       'app/chrome_dll_resource.h',
       'common/automation_constants.h',
       'common/pref_names.cc',
@@ skipping 2899 matching lines @@
         'browser/net/ftp_browsertest.cc',
         'browser/net/load_timing_observer_browsertest.cc',
         'browser/net/proxy_browsertest.cc',
         'browser/notifications/desktop_notifications_unittest.cc',
         'browser/notifications/desktop_notifications_unittest.h',
         'browser/notifications/notification_browsertest.cc',
         'browser/page_cycler/page_cycler_browsertest.cc',
         'browser/performance_monitor/performance_monitor_browsertest.cc',
         'browser/policy/device_management_service_browsertest.cc',
         'browser/policy/policy_browsertest.cc',
+        'browser/policy/policy_prefs_browsertest.cc',
         'browser/popup_blocker_browsertest.cc',
         'browser/prefs/pref_service_browsertest.cc',
         'browser/prerender/prefetch_browsertest.cc',
         'browser/prerender/prerender_browsertest.cc',
         'browser/printing/cloud_print/test/cloud_print_policy_browsertest.cc',
         'browser/printing/cloud_print/test/cloud_print_proxy_process_browsertest.cc',
         'browser/printing/printing_layout_browsertest.cc',
         'browser/printing/print_preview_tab_controller_browsertest.cc',
         'browser/process_singleton_browsertest.cc',
         'browser/profiles/profile_browsertest.cc',
@@ skipping 1819 matching lines @@
                 '--result', '<@(_outputs)',
                 '--isolate', 'browser_tests.isolate',
               ],
             },
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }