ScreenObserver is renamed to BaseScreenDelegate.

chrome/chrome_tests.gypi

 # 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.
 {
   'variables': {
     'chrome_browser_extensions_test_support_sources': [
       # A list of sources which is shared between different browser tests.
       'browser/apps/app_browsertest_util.cc',
       'browser/apps/app_browsertest_util.h',
       'browser/extensions/browsertest_util.cc',
@@ skipping 139 matching lines @@
       'browser/chromeos/login/login_ui_keyboard_browsertest.cc',
       'browser/chromeos/login/login_utils_browsertest.cc',
       'browser/chromeos/login/mixin_based_browser_test.cc',
       'browser/chromeos/login/mixin_based_browser_test.h',
       'browser/chromeos/login/oobe_localization_browsertest.cc',
       'browser/chromeos/login/reset_browsertest.cc',
       # TODO(nkostylev) Re-enable ResourceLoaderBrowserTest.
       #'browser/chromeos/login/resource_loader_browsertest.cc',
       'browser/chromeos/login/saml/saml_browsertest.cc',
       'browser/chromeos/login/session_login_browsertest.cc',
+      'browser/chromeos/login/screens/mock_base_screen_delegate.cc',
+      'browser/chromeos/login/screens/mock_base_screen_delegate.h',
       'browser/chromeos/login/screens/mock_error_screen.cc',
       'browser/chromeos/login/screens/mock_error_screen.h',
       'browser/chromeos/login/screens/mock_eula_screen.cc',
       'browser/chromeos/login/screens/mock_eula_screen.h',
       'browser/chromeos/login/screens/mock_network_screen.cc',
       'browser/chromeos/login/screens/mock_network_screen.h',
-      'browser/chromeos/login/screens/mock_screen_observer.cc',
-      'browser/chromeos/login/screens/mock_screen_observer.h',
       'browser/chromeos/login/screens/mock_update_screen.cc',
       'browser/chromeos/login/screens/mock_update_screen.h',
       'browser/chromeos/login/screens/network_screen_browsertest.cc',
       'browser/chromeos/login/screens/update_screen_browsertest.cc',
       'browser/chromeos/login/supervised/supervised_user_creation_browsertest.cc',
       'browser/chromeos/login/supervised/supervised_user_password_browsertest.cc',
       'browser/chromeos/login/supervised/supervised_user_test_base.cc',
       'browser/chromeos/login/supervised/supervised_user_test_base.h',
       'browser/chromeos/login/signin/oauth2_browsertest.cc',
       'browser/chromeos/login/test/app_window_waiter.cc',
@@ skipping 2991 matching lines @@
             ['enable_webrtc==1', {
               'dependencies': [
                 '../third_party/libjingle/libjingle.gyp:libjingle_webrtc'
               ]
             }],
           ],
         }]
     }],
   ],  # 'conditions'
 }