wptserve: Fix Python process leak on Windows.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/servers/wptserve.py

 # Copyright 2015 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.
 
 """Start and stop the WPTserve servers as they're used by the layout tests."""
 
 from webkitpy.layout_tests.servers import server_base
 
 
 class WPTServe(server_base.ServerBase):
@@ skipping 42 matching lines @@
         self._keep_process_reference = True
         self._start_cmd = start_cmd
 
     def _stop_running_server(self):
         # Clean up the pid file.
         if self._pid and not self._executive.check_running_pid(self._pid):
             self._filesystem.remove(self._pid_file)
             return
 
         # TODO(burnik): Figure out a cleaner way of stopping wptserve.
-        self._executive.interrupt(self._pid)
+        if self._platform.is_win():
+            self._executive.kill_process(self._pid)
+        else:
+            self._executive.interrupt(self._pid)
 
         # According to Popen.wait(), this can deadlock when using stdout=PIPE and/or stderr=PIPE.
         # We're using DEVNULL for both so that should not occur.
         self._process.wait()