Merge apps/pref* to extensions/browser/pref*

apps/apps.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.
 
 {
   'targets': [
     {
       # GN version: //apps
       'target_name': 'apps',
       'type': 'static_library',
@@ skipping 33 matching lines @@
         'app_window_contents.h',
         'app_window_registry.cc',
         'app_window_registry.h',
         'browser_context_keyed_service_factories.cc',
         'browser_context_keyed_service_factories.h',
         'custom_launcher_page_contents.cc',
         'custom_launcher_page_contents.h',
         'launcher.cc',
         'launcher.h',
         'metrics_names.h',
-        'pref_names.cc',
-        'pref_names.h',
-        'prefs.cc',
-        'prefs.h',
         'saved_files_service.cc',
         'saved_files_service.h',
         'saved_files_service_factory.cc',
         'saved_files_service_factory.h',
         'switches.cc',
         'switches.h',
         'ui/apps_client.cc',
         'ui/apps_client.h',
         'ui/views/app_window_frame_view.cc',
         'ui/views/app_window_frame_view.h',
@@ skipping 39 matching lines @@
           'sources/': [
             ['exclude', 'ui/views/'],
           ],
         }],
       ],
       # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
       'msvs_disabled_warnings': [ 4267, ],
     },
   ],  # targets
 }