Add Paths as first-class types in configs.

scripts/slave/recipe_modules/android/config.py

 # Copyright 2013 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.recipe_config import config_item_context, ConfigGroup, Single, List
 from slave.recipe_config import Static
+from slave.recipe_config_types import Path
 
 def BaseConfig(USE_MIRROR=False):
+  chromium_in_android_subpath = ('external', 'chromium_org')
+  build_path = Path('slave_build', ('android-src',))
+
   return ConfigGroup(
     lunch_flavor = Single(basestring),
     repo = ConfigGroup(
       url = Single(basestring),
       branch = Single(basestring),
       sync_flags = List(basestring),
     ),
     USE_MIRROR = Static(bool(USE_MIRROR)),
+
+    # Path stuff
+    chromium_in_android_subpath = Static('/'.join(chromium_in_android_subpath)),
+    build_path = Static(build_path),
+    slave_chromium_in_android_path = Static(
+      build_path(*chromium_in_android_subpath)),
+    slave_android_out_path = Static(build_path('out')),
   )
 
 config_ctx = config_item_context(
   BaseConfig,
   {'USE_MIRROR': (False,)},
   'android')
 
 @config_ctx()
 def AOSP(c):
   c.lunch_flavor = 'full-eng'
   c.repo.url = 'https://android.googlesource.com/platform/manifest'
   c.repo.branch = 'android-4.3_r2.3'
   c.repo.sync_flags = ['-j16', '-d', '-f']