[telemetry] Make default flags passed to WebPageRelay overridable.

chrome/test/functional/webpagereplay.py

 #!/usr/bin/env python
 # 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.
 
 """Start and stop Web Page Replay.
 
 Of the public module names, the following one is key:
   ReplayServer: a class to start/stop Web Page Replay.
 """
@@ skipping 102 matching lines @@
       self._CheckPath('archive directory', os.path.dirname(self.archive_path))
     elif not os.path.exists(self.archive_path):
       self._CheckPath('archive file', self.archive_path)
     self._CheckPath('replay script', self.replay_py)
 
     self.log_fh = None
     self.replay_process = None
 
   def _AddDefaultReplayOptions(self):
     """Set WPR command-line options. Can be overridden if needed."""
-    self.replay_options += [
+    self.replay_options = [
         '--host', str(self._replay_host),
         '--port', str(self._http_port),
         '--ssl_port', str(self._https_port),
         '--use_closest_match',
         '--no-dns_forwarding',
         '--log_level', 'warning'
-        ]
+        ] + self.replay_options
 
   def _CheckPath(self, label, path):
     if not os.path.exists(path):
       raise ReplayNotFoundError(label, path)
 
   def _OpenLogFile(self):
     log_dir = os.path.dirname(self.log_path)
     if not os.path.exists(log_dir):
       os.makedirs(log_dir)
     return open(self.log_path, 'w')
@@ skipping 68 matching lines @@
       self.log_fh.close()
 
   def __enter__(self):
     """Add support for with-statement."""
     self.StartServer()
     return self
 
   def __exit__(self, unused_exc_type, unused_exc_val, unused_exc_tb):
     """Add support for with-statement."""
     self.StopServer()