Remove use of "use_mirror" recipe property.

scripts/tools/run_recipe.py

 #!/usr/bin/python -u
 # 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.
 
 """This allows easy execution of a recipe (scripts/slave/recipes, etc.)
 without buildbot.
 
 This is currently useful for testing recipes locally while developing them.
 
@@ skipping 93 matching lines @@
 
 
 def get_properties_from_file(filename):
   properties_file = sys.stdin if filename == '-' else open(filename)
   return ast.literal_eval(properties_file.read())
 
 
 def main(args):
   """Gets the recipe name and properties and runs an annotated run."""
   properties, master_overrides_slave = parse_args(args)
-  properties.setdefault('use_mirror', False)
 
   if not os.path.exists(SLAVE_DIR):
     os.makedirs(SLAVE_DIR)
 
   env = os.environ.copy()
   env['RUN_SLAVE_UPDATED_SCRIPTS'] = '1'
   env['PYTHONUNBUFFERED'] = '1'
   env['PYTHONIOENCODING'] = 'UTF-8'
 
   cmd = ['python', '-u', RUNIT, 'python', '-u', ANNOTATED_RUN,
          '--keep-stdin',  # so that pdb works for local execution
          '--factory-properties', json.dumps(properties),
          '--build-properties', json.dumps(properties)]
 
   if master_overrides_slave:
     cmd.append('--master-overrides-slave')
 
   return subprocess.call(cmd, cwd=SLAVE_DIR, env=env)
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))