recipe_modules/chromite: Use "build_type".

scripts/slave/recipe_modules/chromite/test_api.py

 # Copyright 2014 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 base64
-import hashlib
+import json
 
 from recipe_engine import recipe_test_api
 
 DEPS = [
     'gitiles',
 ]
 
 class ChromiteTestApi(recipe_test_api.RecipeTestApi):
-  def seed_chromite_config(self, data, branch='master'):
+  def seed_chromite_config(self, data):
     """Seeds step data for the Chromite configuration fetch.
     """
     return self.m.step.step_data('read chromite config',
         self.m.json.output(data))
+
+  def add_chromite_config(self, config_name, build_type=None):
+    d = {
+        config_name: {
+          'build_type': build_type,
+        },
+    }
+    return self.seed_chromite_config(d)