Move recipe engine to third_party/recipe_engine.

scripts/slave/recipe_modules/perf_dashboard/config.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 types
 
-from slave.recipe_config import config_item_context, ConfigGroup
-from slave.recipe_config import Single
+from recipe_engine.config import config_item_context, ConfigGroup
+from recipe_engine.config import Single
 
 def BaseConfig(**_kwargs):
   return ConfigGroup(
     url = Single(basestring)
   )
 
 config_ctx = config_item_context(BaseConfig, {}, 'basic')
 
 @config_ctx()
 def production(c):
   c.url = "https://chromeperf.appspot.com"
 
 @config_ctx()
 def testing(c):
   c.url = "https://chrome-perf.googleplex.com"