Add a Restore() method to ValueStore and make StorageAPI use it

chrome/chrome_tests_unit.gypi

 # Copyright 2012 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.
 {
   'targets': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 879 matching lines @@
         'browser/extensions/api/socket/udp_socket_unittest.cc',
         'browser/extensions/api/sockets_tcp/sockets_tcp_api_unittest.cc',
         'browser/extensions/api/sockets_tcp_server/sockets_tcp_server_api_unittest.cc',
         'browser/extensions/api/sockets_udp/sockets_udp_api_unittest.cc',
         'browser/extensions/api/storage/policy_value_store_unittest.cc',
         'browser/extensions/api/storage/settings_frontend_unittest.cc',
         'browser/extensions/api/storage/settings_quota_unittest.cc',
         'browser/extensions/api/storage/settings_sync_unittest.cc',
         'browser/extensions/api/storage/settings_test_util.cc',
         'browser/extensions/api/storage/settings_test_util.h',
+        'browser/extensions/api/storage/storage_api_unittest.cc',
         'browser/extensions/api/streams_private/streams_private_manifest_unittest.cc',
         'browser/extensions/api/system_display/display_info_provider_chromeos_unittest.cc',
         'browser/extensions/api/web_navigation/frame_navigation_state_unittest.cc',
         'browser/extensions/api/web_request/form_data_parser_unittest.cc',
         'browser/extensions/api/web_request/upload_data_presenter_unittest.cc',
         'browser/extensions/api/web_request/web_request_api_unittest.cc',
         'browser/extensions/api/web_request/web_request_permissions_unittest.cc',
         'browser/extensions/api/web_request/web_request_time_tracker_unittest.cc',
         'browser/extensions/app_sync_data_unittest.cc',
         'browser/extensions/blacklist_unittest.cc',
@@ skipping 1993 matching lines @@
             'browser/ui/app_list/test/fake_profile_store.h',
             'browser/ui/app_list/test/fast_show_pickler_unittest.cc',
             'browser/ui/views/app_list/linux/app_list_linux_unittest.cc',
             'browser/ui/views/app_list/win/app_list_win_unittest.cc',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }