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

build/android/adb_reverse_forwarder.py

 #!/usr/bin/env python
 #
 # Copyright (c) 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.
 
 """Command line tool for forwarding ports from a device to the host.
 
 Allows an Android device to connect to services running on the host machine,
 i.e., "adb forward" in reverse. Requires |host_forwarder| and |device_forwarder|
@@ skipping 38 matching lines @@
     parser.error('Need even number of port pairs')
     sys.exit(1)
 
   try:
     port_pairs = map(int, args[1:])
     port_pairs = zip(port_pairs[::2], port_pairs[1::2])
   except ValueError:
     parser.error('Bad port number')
     sys.exit(1)
 
-  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)
   devices = device_utils.DeviceUtils.HealthyDevices(blacklist)
 
   if options.device:
     device = next((d for d in devices if d == options.device), None)
     if not device:
       raise device_errors.DeviceUnreachableError(options.device)
   elif devices:
     device = devices[0]
     logging.info('No device specified. Defaulting to %s', devices[0])
   else:
     raise device_errors.NoDevicesError()
 
   constants.SetBuildType(options.build_type)
   try:
     forwarder.Forwarder.Map(port_pairs, device)
     while True:
       time.sleep(60)
   except KeyboardInterrupt:
     sys.exit(0)
   finally:
     forwarder.Forwarder.UnmapAllDevicePorts(device)
 
 if __name__ == '__main__':
   main(sys.argv)