Build chromedriver2_unittests as part of chromium_builder_tests.

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 700 matching lines @@
         'test/chromedriver/command_executor_impl_unittest.cc',
         'test/chromedriver/commands_unittest.cc',
         'test/chromedriver/fake_session_accessor.cc',
         'test/chromedriver/fake_session_accessor.h',
         'test/chromedriver/session_command_unittest.cc',
         'test/chromedriver/session_unittest.cc',
         'test/chromedriver/status_unittest.cc',
         'test/chromedriver/synchronized_map_unittest.cc',
       ],
     },
-    # ChromeDriver2 tests that aren't run on the main buildbots.
+    # ChromeDriver2 tests that aren't run on the main buildbot. Available
+    # as an optional test type on trybots.
     {
       'target_name': 'chromedriver2_tests',
       'type': 'executable',
       'dependencies': [
         'chromedriver2_lib',
         '../base/base.gyp:base',
         '../base/base.gyp:run_all_unittests',
         '../build/temp_gyp/googleurl.gyp:googleurl',
         '../net/net.gyp:http_server',
         '../net/net.gyp:net',
@@ skipping 2131 matching lines @@
             'sync_integration_tests.isolate',
           ],
           'sources': [
             'sync_integration_tests.isolate',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }