When killing wptserve, use Executive.interrupt on non-Windows platforms.

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 134 matching lines @@
 
     def cpu_count(self):
         return 2
 
     def kill_all(self, process_name):
         pass
 
     def kill_process(self, pid):
         pass
 
+    def interrupt(self, pid):
+        pass
+
     def popen(self, args, cwd=None, env=None, **_):
         assert all(isinstance(arg, basestring) for arg in args)
         self.calls.append(args)
         if self._should_log:
             cwd_string = ""
             if cwd:
                 cwd_string = ", cwd=%s" % cwd
             env_string = ""
             if env:
                 env_string = ", env=%s" % env
@@ skipping 19 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 []