[devil] Extract logging common behavior to its own module.

devil/devil/utils/logging_common.py

-# Copyright (c) 2012 The Chromium Authors. All rights reserved.
+# Copyright 2017 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.
 
-"""Helper functions common to native, java and host-driven test runners."""
-
 import logging
 import sys
 import time
 
 
+def AddLoggingArguments(parser):
+  parser.add_argument(
+      '-v', '--verbose', action='count', default=0,
+      help='Log more. Use multiple times for even more logging.')
+
+
+def InitializeLogging(args, handler=None):
+  if args.verbose == 0:
+    log_level = logging.WARNING
+  elif args.verbose == 1:
+    log_level = logging.INFO
+  else:
+    log_level = logging.DEBUG
+  logger = logging.getLogger()
+  logger.setLevel(log_level)
+  if not handler:
+    handler = logging.StreamHandler(sys.stdout)
+    handler.setFormatter(CustomFormatter())
+  logger.addHandler(handler)
+
+
 class CustomFormatter(logging.Formatter):
   """Custom log formatter."""
 
   # override
   def __init__(self, fmt='%(threadName)-4s  %(message)s'):
     # Can't use super() because in older Python versions logging.Formatter does
     # not inherit from object.
     logging.Formatter.__init__(self, fmt=fmt)
     self._creation_time = time.time()
 
   # override
   def format(self, record):
     # Can't use super() because in older Python versions logging.Formatter does
     # not inherit from object.
     msg = logging.Formatter.format(self, record)
     if 'MainThread' in msg[:19]:
       msg = msg.replace('MainThread', 'Main', 1)
     timediff = time.time() - self._creation_time
     return '%s %8.3fs %s' % (record.levelname[0], timediff, msg)
 
-
-def SetLogLevel(verbose_count, add_handler=True):
-  """Sets log level as |verbose_count|.
-
-  Args:
-    verbose_count: Verbosity level.
-    add_handler: If true, adds a handler with |CustomFormatter|.
-  """
-  log_level = logging.WARNING  # Default.
-  if verbose_count == 1:
-    log_level = logging.INFO
-  elif verbose_count >= 2:
-    log_level = logging.DEBUG
-  logger = logging.getLogger()
-  logger.setLevel(log_level)
-  if add_handler:
-    custom_handler = logging.StreamHandler(sys.stdout)
-    custom_handler.setFormatter(CustomFormatter())
-    logging.getLogger().addHandler(custom_handler)