Take out and generalize user prefs overriding from IncognitoUserPrefStore.

chrome/chrome_tests.gypi

 # Copyright (c) 2011 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.
 {
   'variables' : {
     # Variables for js2gtest rules
     'gypv8sh': '../tools/gypv8sh.py',
     'js2gtest': 'test/base/js2gtest.js',
     'js2gtest_out_dir': '<(SHARED_INTERMEDIATE_DIR)/js2gtest',
     'mock_js': 'third_party/mock4js/mock4js.js',
@@ skipping 1483 matching lines @@
         'browser/policy/testing_cloud_policy_subsystem.cc',
         'browser/policy/testing_cloud_policy_subsystem.h',
         'browser/policy/testing_policy_url_fetcher_factory.cc',
         'browser/policy/testing_policy_url_fetcher_factory.h',
         'browser/policy/url_blacklist_manager_unittest.cc',
         'browser/policy/user_policy_cache_unittest.cc',
         'browser/preferences_mock_mac.cc',
         'browser/preferences_mock_mac.h',
         'browser/prefs/command_line_pref_store_unittest.cc',
         'browser/prefs/incognito_mode_prefs_unittest.cc',
-        'browser/prefs/incognito_user_pref_store_unittest.cc',
+        'browser/prefs/overlay_user_pref_store_unittest.cc',
         'browser/prefs/pref_change_registrar_unittest.cc',
         'browser/prefs/pref_member_unittest.cc',
         'browser/prefs/pref_model_associator_unittest.cc',
         'browser/prefs/pref_notifier_impl_unittest.cc',
         'browser/prefs/pref_service_unittest.cc',
         'browser/prefs/pref_set_observer_unittest.cc',
         'browser/prefs/pref_value_map_unittest.cc',
         'browser/prefs/pref_value_store_unittest.cc',
         'browser/prefs/proxy_config_dictionary_unittest.cc',
         'browser/prefs/proxy_policy_unittest.cc',
@@ skipping 2710 matching lines @@
               # Use outputs of this action as inputs for the main target build.
               # Seems as a misnomer but makes this happy on Linux (scons).
               'process_outputs_as_sources': 1,
             },
           ],  # 'actions'
         },
       ]
     }],  # 'coverage!=0'
   ],  # 'conditions'
 }