Remove the overridden _stop_running_server method in WPTServe.

third_party/WebKit/Tools/Scripts/webkitpy/common/system/executive_mock.py

 # Copyright (C) 2011 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 42 matching lines @@
             return None
         return self.returncode
 
     def communicate(self, *_):
         return (self.stdout.getvalue(), self.stderr.getvalue())
 
 
 class MockExecutive(object):
     PIPE = "MOCK PIPE"
     STDOUT = "MOCK STDOUT"
+    DEVNULL = "MOCK_DEVNULL"
 
     @staticmethod
     def ignore_error(error):
         pass
 
     def __init__(self, should_log=False, should_throw=False,
                  output="MOCK output of child process", stderr='',
                  exit_code=0, exception=None, run_command_fn=None):
         self._should_log = should_log
         self._should_throw = should_throw
@@ skipping 110 matching lines @@
         new_calls = self.calls[num_previous_calls:]
         self.calls = self.calls[:num_previous_calls]
         self.calls.append(new_calls)
         return command_outputs
 
     def map(self, thunk, arglist, processes=None):
         return map(thunk, arglist)
 
     def process_dump(self):
         return []