Break config_default into master_site_configs.

masters/master.client.nacl.chrome/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 'nacl' 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 12 matching lines @@
 
 from buildbot.changes import svnpoller
 from buildbot.scheduler import Scheduler
 from buildbot.scheduler import Triggerable
 
 from master import master_utils
 from master import slaves_list
 from master.factory import chromium_factory
 
 import config
+import master_site_config
 
-ActiveMaster = config.Master.NativeClientChrome
+ActiveMaster = master_site_config.NativeClientChrome
 
 TREE_GATE_KEEPER = False
 GOOD_REVISIONS = False
 
 # This is the dictionary that the buildmaster pays attention to. We also use
 # a shorter alias to save typing.
 c = BuildmasterConfig = {}
 
 config.DatabaseSetup(c, require_dbconfig=ActiveMaster.is_production_host)
 
@@ skipping 252 matching lines @@
   ]
   c['status'].append(goodrevisions.GoodRevisions(
       good_revision_steps={'': all_steps},
       store_revisions_url=ActiveMaster.store_revisions_url))
 
 
 ####### PROJECT IDENTITY
 
 # Buildbot master url:
 c['buildbotURL'] = 'http://build.chromium.org/p/client.nacl.chrome/'