Add Xvfb debugging code to run-webkit-tests.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.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 339 matching lines @@
         Returns:
             An exit status code.
         """
         cmd = [self._path_to_driver(), '--check-layout-test-sys-deps']
 
         local_error = ScriptError()
 
         def error_handler(script_error):
             local_error.exit_code = script_error.exit_code
 
+        _log.warn('DISPLAY = %s', self.host.environ['DISPLAY'])

[mithro, 2017/04/26 01:58:33]

This needs to be self.host.environ.get('DISPLAY', None) or similar (see your
failing bot).

[Dirk Pranke, 2017/04/26 02:03:00]

ah, yeah :).

         output = self._executive.run_command(cmd, error_handler=error_handler)
         if local_error.exit_code:
             _log.error('System dependencies check failed.')
             _log.error('To override, invoke with --nocheck-sys-deps')
             _log.error('')
             _log.error(output)
             if self.BUILD_REQUIREMENTS_URL is not '':
                 _log.error('')
                 _log.error('For complete build requirements, please see:')
                 _log.error(self.BUILD_REQUIREMENTS_URL)
@@ skipping 1261 matching lines @@
 
     def __init__(self, base, args, reference_args=None):
         self.name = base
         self.base = base
         self.args = args
         self.reference_args = args if reference_args is None else reference_args
         self.tests = set()
 
     def __repr__(self):
         return "PhysicalTestSuite('%s', '%s', %s, %s)" % (self.name, self.base, self.args, self.reference_args)