Add simple depends_on API.

recipe_engine/recipe_api.py

 # Copyright 2013-2015 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.
 
 from __future__ import absolute_import
 import contextlib
+import json
 import keyword
+import os
 import re
+import subprocess
+import tempfile
 import types
 
 from functools import wraps
 
 from .recipe_test_api import DisabledTestData, ModuleTestData
 from .config import Single
 
 from .util import ModuleInjectionSite
 
 from . import field_composer
@@ skipping 428 matching lines @@
   @property
   def name(self):
     return self._module.NAME
 
 
 class RecipeApi(RecipeApiPlain):
   __metaclass__ = RecipeApiMeta
 
 
 class RecipeScriptApi(RecipeApiPlain, ModuleInjectionSite):
-  pass
+  def depend_on(self, recipe, properties):
+    recipe_script = self._engine._universe.load_recipe(recipe)
+    return recipe_script.run(self, properties)
 
 
 # This is a sentinel object for the Property system. This allows users to
 # specify a default of None that will actually be respected.
 PROPERTY_SENTINEL = object()
 
 class BoundProperty(object):
   """
   A bound, named version of a Property.
 
@@ skipping 160 matching lines @@
     """
     Gets the BoundProperty version of this Property. Requires a name.
     """
     return BoundProperty(
         self._default, self.help, self.kind, name, property_type, module,
         self.param_name)
 
 class UndefinedPropertyException(TypeError):
   pass