Add Paths as first-class types in configs.

scripts/slave/recipe_modules/chromium_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
 from slave.recipe_config import Dict, Single, Static
+from slave.recipe_config_types import Path
 
 def BaseConfig(INTERNAL, REPO_NAME, REPO_URL, **_kwargs):
   return ConfigGroup(
     INTERNAL = Static(INTERNAL),
     REPO_NAME = Static(REPO_NAME),
     REPO_URL = Static(REPO_URL),
     target_arch = Single(basestring, required=False, empty_val=''),
-    extra_env = Dict(value_type=(basestring,int,list)),
+    extra_env = Dict(value_type=(basestring,int,Path)),
     run_findbugs = Single(bool, required=False, empty_val=False),
     run_lint = Single(bool, required=False, empty_val=False),
     run_checkdeps = Single(bool, required=False, empty_val=False),
-    apply_svn_patch = Single(bool, required=False, empty_val=False)
+    apply_svn_patch = Single(bool, required=False, empty_val=False),
+    build_internal_android = Static(Path('build_internal',
+                                         ('scripts', 'slave', 'android')))
   )
 
 
 VAR_TEST_MAP = {
   'INTERNAL': [True, False],
   'REPO_NAME': ['src', 'internal'],
   'REPO_URL': ['bob_dot_org', 'mike_dot_org'],
 }
 
 def TEST_NAME_FORMAT(kwargs):
@@ skipping 21 matching lines @@
   pass
 
 @config_ctx()
 def x86_builder(c):
   c.target_arch = 'x86'
 
 @config_ctx()
 def klp_builder(c):
   c.extra_env = {
     'ANDROID_SDK_BUILD_TOOLS_VERSION': 'android-KeyLimePie',
-    'ANDROID_SDK_ROOT': ['third_party', 'android_tools_internal', 'sdk'],
+    'ANDROID_SDK_ROOT': Path(
+      'checkout', ('third_party', 'android_tools_internal', 'sdk')),
     'ANDROID_SDK_VERSION': 'KeyLimePie'
   }
 
 @config_ctx()
 def try_builder(c):
   if c.INTERNAL:
     c.apply_svn_patch = True
     c.run_findbugs = True
     c.run_lint = True
 
 @config_ctx(includes=['x86_builder', 'try_builder'])
 def x86_try_builder(c):
   pass