Add BuildBucket manifest scheduling support.

scripts/slave/recipe_modules/chromite/config.py

 # Copyright 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.
 
 import os
 import types
 
 from recipe_engine.config import config_item_context, ConfigGroup
 from recipe_engine.config import Dict, Single, Set
 
 
 def BaseConfig(CBB_CONFIG=None, CBB_BRANCH=None, CBB_BUILD_NUMBER=None,
                CBB_DEBUG=False, CBB_CLOBBER=False, CBB_BUILDBUCKET_ID=None,
-               **_kwargs):
+               CBB_MASTER_BUILD_ID=None, **_kwargs):
   return ConfigGroup(
     # Base mapping of repository key to repository name.
     repositories = Dict(value_type=Set(basestring)),
 
     # Checkout Chromite at this branch. "origin/" will be prepended.
     chromite_branch = Single(basestring, empty_val=CBB_BRANCH or 'master'),
 
     # Should the Chrome version be supplied to cbuildbot?
     use_chrome_version = Single(bool),
 
@@ skipping 15 matching lines @@
 
     # cbuildbot tool flags.
     cbb = ConfigGroup(
       # The Chromite configuration to use.
       config = Single(basestring, empty_val=CBB_CONFIG),
 
       # The buildroot directory name to use.
       builddir = Single(basestring),
 
       # If supplied, forward to cbuildbot as '--master-build-id'.
-      build_id = Single(basestring),
+      build_id = Single(basestring, empty_val=CBB_MASTER_BUILD_ID),
 
       # If supplied, forward to cbuildbot as '--buildnumber'.
       build_number = Single(int, empty_val=CBB_BUILD_NUMBER),
 
       # If supplied, forward to cbuildbot as '--chrome-rev'.
       chrome_rev = Single(basestring),
 
       # If supplied, forward to cbuildbot as '--chrome_version'.
       chrome_version = Single(basestring),
 
@@ skipping 108 matching lines @@
 def chromiumos_coverage(c):
   c.use_chrome_version = True
   c.read_cros_manifest = True
   c.cbb.chrome_rev = 'stable'
   c.cbb.config_repo = 'https://example.com/repo.git'
 
 # TODO(dnj): Remove this config once variant support is removed.
 @config_ctx()
 def coverage_variant(c):
   c.cbb.chrome_rev = 'canary'