Move recipe engine to third_party/recipe_engine.

scripts/slave/recipe_modules/url/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.
 
-from slave import recipe_api
+from recipe_engine import recipe_api
 
 import urllib
 
 class UrlApi(recipe_api.RecipeApi):
   urlencode = staticmethod(urllib.urlencode)
 
   @recipe_api.non_step
   def join(self, *parts):
     return '/'.join(str(x).strip('/') for x in parts)
 
   def fetch(self, url, step_name=None, attempts=None, **kwargs):
     if not step_name:
       step_name = 'fetch %s' % url
     args = [
         url,
         '--outfile', self.m.raw_io.output(),
     ]
     if attempts:
       args.extend(['--attempts', attempts])
     fetch_result = self.m.python(
         name=step_name,
         script=self.m.path['build'].join('scripts', 'tools', 'pycurl.py'),
         args=args,
         **kwargs)
     return fetch_result.raw_io.output