Revert of Remove unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/common/message_pool.py

 # Copyright (C) 2011 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 # copyright notice, this list of conditions and the following disclaimer
@@ skipping 27 matching lines @@
 If you don't need these features, use multiprocessing.Pool or concurrency.futures
 intead.
 
 """
 
 import cPickle
 import logging
 import multiprocessing
 import Queue
 import sys
+import time
 import traceback
 
 
 from webkitpy.common.host import Host
 from webkitpy.common.system import stack_utils
 
 
 _log = logging.getLogger(__name__)
 
 
@@ skipping 258 matching lines @@
 
 
 class _WorkerLogHandler(logging.Handler):
     def __init__(self, worker):
         logging.Handler.__init__(self)
         self._worker = worker
         self.setLevel(worker.log_level)
 
     def emit(self, record):
         self._worker.log_messages.append(record)