build: use class path bases, not strings

scripts/slave/recipe_modules/chromium_android/api.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.
 
 import contextlib
 import datetime
 import json
 import os
 import re
 import urllib
 
 from recipe_engine.types import freeze
 from recipe_engine import recipe_api
 
 
 def _TimestampToIsoFormat(timestamp):
   return datetime.datetime.utcfromtimestamp(timestamp).strftime('%Y%m%dT%H%M%S')
 
 
 class AndroidApi(recipe_api.RecipeApi):
   def __init__(self, **kwargs):
     super(AndroidApi, self).__init__(**kwargs)
     self._devices = None
     self._file_changes_path = None
 
   def get_config_defaults(self):
     return {
-      'REVISION': self.m.properties.get('revision', '')
+      'REVISION': self.m.properties.get('revision', ''),
+      'CHECKOUT_PATH': self.m.path['checkout'],
     }
 
   @property
   def devices(self):
     assert self._devices is not None,\
         'devices is only available after device_status_check()'
     return self._devices
 
   @property
   def out_path(self):
@@ skipping 1224 matching lines @@
       script = self.c.test_runner
       if wrapper_script_suite_name:
         script = self.m.chromium.output_dir.join('bin', 'run_%s' %
                                                  wrapper_script_suite_name)
       else:
         env = kwargs.get('env', {})
         env['CHROMIUM_OUTPUT_DIR'] = env.get('CHROMIUM_OUTPUT_DIR',
                                              self.m.chromium.output_dir)
         kwargs['env'] = env
       return self.m.python(step_name, script, args, **kwargs)