[Android] Don't use a device blacklist if one isn't provided.

build/android/tombstones.py

 #!/usr/bin/env python
 #
 # Copyright 2013 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.
 #
 # Find the most recent tombstone file(s) on all connected devices
 # and prints their stacks.
 #
 # Assumes tombstone file was created with current symbols.
@@ skipping 219 matching lines @@
   parser.add_option('-s', '--stack', action='store_true',
                     help='Also include symbols for stack data')
   parser.add_option('-w', '--wipe-tombstones', action='store_true',
                     help='Erase all tombstones from device after processing')
   parser.add_option('-j', '--jobs', type='int',
                     default=4,
                     help='Number of jobs to use when processing multiple '
                          'crash stacks.')
   options, _ = parser.parse_args()
 
-  if options.blacklist_file:
-    blacklist = device_blacklist.Blacklist(options.blacklist_file)
-  else:
-    blacklist = None
+  blacklist = (device_blacklist.Blacklist(options.blacklist_file)
+               if options.blacklist_file
+               else None)
 
   if options.device:
     devices = [device_utils.DeviceUtils(options.device)]
   else:
     devices = device_utils.DeviceUtils.HealthyDevices(blacklist)
 
   # This must be done serially because strptime can hit a race condition if
   # used for the first time in a multithreaded environment.
   # http://bugs.python.org/issue7980
   tombstones = []
   for device in devices:
     tombstones += _GetTombstonesForDevice(device, options)
 
   _ResolveTombstones(options.jobs, tombstones)
 
 
 if __name__ == '__main__':
   sys.exit(main())