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

build/android/update_verification.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.
 
 """Runs semi-automated update testing on a non-rooted device.
 
 This script will help verify that app data is preserved during an update.
 To use this script first run it with the create_app_data option.
@@ skipping 72 matching lines @@
   subparser.add_argument('--new-apk', required=True,
                          help='Path to apk to update to.')
   subparser.add_argument('--app-data', required=True,
                          help='Path to where the app data backup is saved.')
   subparser.add_argument('--package-name',
                          help='Chrome apk package name.')
 
   args = parser.parse_args()
   run_tests_helper.SetLogLevel(args.verbose)
 
-  if args.blacklist_file:
-    blacklist = device_blacklist.Blacklist(args.blacklist_file)
-  else:
-    blacklist = None
+  blacklist = (device_blacklist.Blacklist(args.blacklist_file)
+               if args.blacklist_file
+               else None)
 
   devices = device_utils.DeviceUtils.HealthyDevices(blacklist)
   if not devices:
     raise device_errors.NoDevicesError()
   device = devices[0]
   logging.info('Using device %s for testing.' % str(device))
 
   package_name = (args.package_name if args.package_name
                   else apk_helper.GetPackageName(args.old_apk))
   if args.command == 'create_app_data':
     CreateAppData(device, args.old_apk, args.app_data, package_name)
   elif args.command == 'test_update':
     TestUpdate(
         device, args.old_apk, args.new_apk, args.app_data, package_name)
   else:
     raise Exception('Unknown test command: %s' % args.command)
 
 if __name__ == '__main__':
   sys.exit(main())