[Android] Add a configurable environment for devil/.

build/android/devil/android/sdk/shared_prefs_test.py

 #!/usr/bin/env python
 # Copyright 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.
 
 """
 Unit tests for the contents of shared_prefs.py (mostly SharedPrefs).
 """
 
 import logging
-import os
 import sys
 import unittest
 
+from devil import devil_env
 from devil.android import device_utils
 from devil.android.sdk import shared_prefs
-from pylib import constants
 
-sys.path.append(os.path.join(
-    constants.DIR_SOURCE_ROOT, 'third_party', 'pymock'))
+sys.path.append(devil_env.config.pymock_path)
 import mock # pylint: disable=import-error
 
 
 def MockDeviceWithFiles(files=None):
   if files is None:
     files = {}
 
   def file_exists(path):
     return path in files
 
@@ skipping 129 matching lines @@
 
     self.assertEquals(self.device.WriteFile.call_args_list, []) # did not write
     with shared_prefs.SharedPrefs(
         self.device, 'com.some.package', 'prefs.xml') as prefs:
       # contents were not modified
       self.assertEquals(prefs.AsDict(), self.expected_data)
 
 if __name__ == '__main__':
   logging.getLogger().setLevel(logging.DEBUG)
   unittest.main(verbosity=2)