Allow unit tests to force serial execution in the test launcher.

ui/base/ui_base_tests.gyp

 # Copyright 2013 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': {
     'chromium_code': 1,
   },
   'targets': [
     {
@@ skipping 33 matching lines @@
         'resource/data_pack_literal.cc',
         'resource/data_pack_unittest.cc',
         'resource/resource_bundle_unittest.cc',
         'test/run_all_unittests.cc',
       ],
       'all_sources': [
         # Note: file list duplicated in GN build.
         '<@(_common_sources)',
         'accelerators/accelerator_manager_unittest.cc',
         'accelerators/menu_label_accelerator_util_linux_unittest.cc',
+        'clipboard/clipboard_unittest.cc',
         'clipboard/custom_data_helper_unittest.cc',
         'cocoa/base_view_unittest.mm',
         'cocoa/cocoa_base_utils_unittest.mm',
         'cocoa/controls/blue_label_button_unittest.mm',
         'cocoa/controls/hover_image_menu_button_unittest.mm',
         'cocoa/controls/hyperlink_button_cell_unittest.mm',
         'cocoa/controls/hyperlink_text_view_unittest.mm',
         'cocoa/focus_tracker_unittest.mm',
         'cocoa/fullscreen_window_manager_unittest.mm',
         'cocoa/hover_image_button_unittest.mm',
@@ skipping 233 matching lines @@
               'dependencies': [
                 '../../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }