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

devil/devil/utils/logging_common.py

Index: devil/devil/utils/logging_common.py
diff --git a/devil/devil/utils/logging_common.py b/devil/devil/utils/logging_common.py
new file mode 100644
index 0000000000000000000000000000000000000000..5aea3c64eeec742256a04f952afaffb98f5f657a
--- /dev/null
+++ b/devil/devil/utils/logging_common.py
@@ -0,0 +1,50 @@
+# 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.
+
+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)
+