Use exit command to stop web page replay server.

tools/telemetry/telemetry/core/wpr_server.py

 # Copyright (c) 2012 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.
 
 from telemetry.core import util
 
 # TODO(tonyg): Move webpagereplay.py to a common location.
 util.AddDirToPythonPath(
     util.GetChromiumSrcDir(), 'chrome', 'test', 'functional')
 import webpagereplay  # pylint: disable=F0401
 
+
 def GetChromeFlags(replay_host, http_port, https_port):
   return webpagereplay.GetChromeFlags(replay_host, http_port, https_port)
 
-class _WebPageReplayServer(webpagereplay.ReplayServer): # pylint: disable=W0232
+
+class _WebPageReplayServer(webpagereplay.ReplayServer):  # pylint: disable=W0232
   def _AddDefaultReplayOptions(self):
-    """Override. Because '--no-dns_forwarding' is added by default in parent
-       while webdriver-based backends need dns forwarding."""
+    """Override to avoid adding 'no-dns_forwarding' by default.
+
+      Webdriver-based backends need dns forwarding.
+    """
     self.replay_options += [
         '--port', str(self._http_port),
         '--ssl_port', str(self._https_port),
         '--use_closest_match',
         '--log_level', 'warning'
         ]
 
+
 class ReplayServer(object):
   def __init__(self, browser_backend, path, is_record_mode, is_append_mode,
                make_javascript_deterministic, webpagereplay_host,
                webpagereplay_local_http_port, webpagereplay_local_https_port,
                webpagereplay_remote_http_port, webpagereplay_remote_https_port):
     self._browser_backend = browser_backend
     self._forwarder = None
     self._web_page_replay = None
     self._is_record_mode = is_record_mode
     self._is_append_mode = is_append_mode
@@ skipping 32 matching lines @@
   def __exit__(self, *args):
     self.Close()
 
   def Close(self):
     if self._forwarder:
       self._forwarder.Close()
       self._forwarder = None
     if self._web_page_replay:
       self._web_page_replay.StopServer()
       self._web_page_replay = None