wptserve: Do not drop environment variables on running 'serve' command.

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 30 matching lines @@
         # TODO(burnik): Merge with default start_cmd once we roll in websockets.
         if self._port_obj.host.filesystem.exists(path_to_ws_handlers):
             start_cmd += ['--ws_doc_root', path_to_ws_handlers]
 
         # TODO(tkent): Do not suppress console output on Windows until
         # crbug.com/623613 is resolved.
         if not self._platform.is_win():
             self._stdout = self._stderr = self._executive.DEVNULL
         # TODO(burnik): We should stop setting the CWD once WPT can be run without it.
         self._cwd = path_to_wpt_root
-        self._env = {'PYTHONPATH': path_to_thirdparty}
+        self._env = port_obj.host.environ.copy()
+        self._env.update({'PYTHONPATH': path_to_thirdparty})
         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)
 
         # 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()