Add simple depends_on API.

recipe_engine/lint_test.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Tests that recipes are on their best behavior.
 
 Checks that recipes only import modules from a whitelist.  Imports are
 generally not safe in recipes if they depend on the platform, since
 e.g. you can run a recipe simulation for a Windows recipe on Linux.
@@ skipping 43 matching lines @@
       module_name = val.__name__
       for pattern in whitelist:
         if pattern.match(val.__name__):
           break
       else:
         yield ('In %s:\n'
                '  Non-whitelisted import of %s' %
                (recipe_path, module_name))
 
 
-def main(package_deps, whitelist=[]):
+def main(universe, whitelist=[]):
   from . import loader
   from . import package
 
   whitelist = map(re.compile, MODULES_WHITELIST + whitelist)
-  universe = loader.RecipeUniverse(package_deps)
 
   errors = []
   for recipe_path, recipe_name in universe.loop_over_recipes():
     errors.extend(ImportsTest(recipe_path, recipe_name, whitelist, universe))
 
   if errors:
     raise TestFailure('\n'.join(map(str, errors)))