Avoid crashing due to missing trace_output option in Monkey test

build/android/pylib/local/device/local_device_environment.py

 # Copyright 2014 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.
 
 import datetime
 import functools
 import logging
 import os
 import shutil
 import tempfile
@@ skipping 76 matching lines @@
     self._devices = None
     self._concurrent_adb = args.enable_concurrent_adb
     self._enable_device_cache = args.enable_device_cache
     self._logcat_monitors = []
     self._logcat_output_dir = args.logcat_output_dir
     self._logcat_output_file = args.logcat_output_file
     self._max_tries = 1 + args.num_retries
     self._skip_clear_data = args.skip_clear_data
     self._target_devices_file = args.target_devices_file
     self._tool_name = args.tool
-    self._trace_output = args.trace_output
+    self._trace_output = None
+    if hasattr(args, 'trace_output'):
+      self._trace_output = args.trace_output
 
     devil_chromium.Initialize(
         output_directory=constants.GetOutDirectory(),
         adb_path=args.adb_path)
 
     # Some things such as Forwarder require ADB to be in the environment path.
     adb_dir = os.path.dirname(adb_wrapper.AdbWrapper.GetAdbPath())
     if adb_dir and adb_dir not in os.environ['PATH'].split(os.pathsep):
       os.environ['PATH'] = adb_dir + os.pathsep + os.environ['PATH']
 
@@ skipping 160 matching lines @@
     else:
       trace_event.trace_disable()
     self._JsonToTrace(self._trace_output + '.json',
                       self._trace_output)
 
   def EnableTracing(self):
     if trace_event.trace_is_enabled():
       logging.warning('Tracing is already running.')
     else:
       trace_event.trace_enable(self._trace_output + '.json')