Break config_default into master_site_configs.

masters/master.chromium.perf/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 'chromium' 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 16 matching lines @@
 from buildbot.scheduler import Triggerable
 
 from master import build_utils
 from master import chromium_notifier
 from master import master_config
 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.ChromiumPerf
+ActiveMaster = master_site_config.ChromiumPerf
 
 # Enable MAIL_NOTIFIER in production to send perf sheriff alerts.
 MAIL_NOTIFIER = 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 = {}
 
 # 'slavePortnum' defines the TCP port to listen on. This must match the value
 # configured into the buildslaves (with their --master option)
@@ skipping 1004 matching lines @@
 c['projectName'] = ActiveMaster.project_name
 c['projectURL'] = config.Master.project_url
 
 # the 'buildbotURL' string should point to the location where the buildbot's
 # internal web server (usually the html.Waterfall page) is visible. This
 # typically uses the port number set in the Waterfall 'status' entry, but
 # with an externally-visible host name which the buildbot cannot figure out
 # without some help.
 
 c['buildbotURL'] = 'http://build.chromium.org/p/chromium.perf/'