Add Paths as first-class types in configs.

scripts/slave/recipe_api.py

Index: scripts/slave/recipe_api.py
diff --git a/scripts/slave/recipe_api.py b/scripts/slave/recipe_api.py
index 06d2cfac0ae5afd13036426a5ff46546bac5a643..ee74029dfa1306f0a68be306c3db80b7ed9de4a2 100644
--- a/scripts/slave/recipe_api.py
+++ b/scripts/slave/recipe_api.py
@@ -44,7 +44,7 @@ class RecipeApi(object):
     """Returns a 'config blob' for the current API."""
     return self.make_config_params(config_name, optional, **CONFIG_VARS)[0]
 
-  def make_config_params(self, config_name=None, optional=False, **CONFIG_VARS):
+  def make_config_params(self, config_name, optional=False, **CONFIG_VARS):
     """Returns a 'config blob' for the current API, and the computed params
     for all dependent configurations.
 
@@ -85,17 +85,20 @@ class RecipeApi(object):
       else:
         raise  # TODO(iannucci): raise a better exception.
 
-  def set_config(self, config_name, optional=False, **CONFIG_VARS):
+  def set_config(self, config_name=None, optional=False, include_deps=True,
+                 **CONFIG_VARS):
     """Sets the modules and its dependencies to the named configuration."""
     assert self._module
     config, params = self.make_config_params(config_name, optional,
                                              **CONFIG_VARS)
     if config:
       self.c = config
-    # TODO(iannucci): This is 'inefficient', since if a dep comes up multiple
-    # times in this recursion, it will get set_config()'d multiple times
-    for dep in self._module.DEPS:
-      getattr(self.m, dep).set_config(config_name, optional=True, **params)
+
+    if include_deps:
+      # TODO(iannucci): This is 'inefficient', since if a dep comes up multiple
+      # times in this recursion, it will get set_config()'d multiple times
+      for dep in self._module.DEPS:
+        getattr(self.m, dep).set_config(config_name, optional=True, **params)
 
   def apply_config(self, config_name, config_object=None):
     """Apply a named configuration to the provided config object or self."""