Break config_default into master_site_configs.

masters/master.chromiumos/master.cfg

 # -*- python -*-
 # ex: set syntax=python:
 
 # Copyright (c) 2012 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 is the buildmaster config file for the 'chromeos' bot. It must
 # be installed as 'master.cfg' in your buildmaster's base directory
 # (although the filename can be changed with the --basedir option to
@@ skipping 10 matching lines @@
 from buildbot.scheduler import Periodic
 
 # These modules come from scripts/master, which must be in the PYTHONPATH.
 from master import master_utils
 from master import slaves_list
 from master.cros_filter import FilterNewSpec
 from master.factory import chromeos_factory
 
 # These modules come from scripts/common, which must be in the PYTHONPATH.
 import config
+import master_site_config
 
-ActiveMaster = config.Master.ChromiumOS
+ActiveMaster = master_site_config.ChromiumOS
 
 TREE_GATE_KEEPER = ActiveMaster.is_production_host
 
 # Never enable auto_reboot for folks testing locally.
 DISABLE_AUTO_REBOOT = not ActiveMaster.is_production_host
 
 # This is the dictionary that the buildmaster pays attention to. We also use
 # a shorter alias to save typing.
 c = BuildmasterConfig = {}
 
@@ skipping 252 matching lines @@
       extraRecipients=['chrome-troopers@google.com'],
       sheriffs=['sheriff'],
       lookup=master_utils.FilterDomain(),
       use_getname=True))
 
 
 ####### PROJECT IDENTITY
 
 # Buildbot master url:
 c['buildbotURL'] = 'http://build.chromium.org/buildbot/chromiumos/'