Cleanup: Pull some browser keep alive functions into its own file.

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 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_chromeos_sources': [
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.cc',
       'browser/extensions/api/cast_devices_private/cast_devices_private_api.h',
       'browser/extensions/api/certificate_provider/certificate_provider_api.cc',
@@ skipping 68 matching lines @@
       'browser/apps/ephemeral_app_service.cc',
       'browser/apps/ephemeral_app_service.h',
       'browser/apps/ephemeral_app_service_factory.cc',
       'browser/apps/ephemeral_app_service_factory.h',
       'browser/apps/install_chrome_app.cc',
       'browser/apps/install_chrome_app.h',
       'browser/apps/per_app_settings_service.cc',
       'browser/apps/per_app_settings_service.h',
       'browser/apps/per_app_settings_service_factory.cc',
       'browser/apps/per_app_settings_service_factory.h',
-      'browser/apps/scoped_keep_alive.cc',
-      'browser/apps/scoped_keep_alive.h',
       'browser/apps/shortcut_manager.cc',
       'browser/apps/shortcut_manager.h',
       'browser/apps/shortcut_manager_factory.cc',
       'browser/apps/shortcut_manager_factory.h',
       'browser/copresence/chrome_whispernet_client.cc',
       'browser/copresence/chrome_whispernet_client.h',
       'browser/copresence/chrome_whispernet_config.h',
       'browser/extensions/active_install_data.cc',
       'browser/extensions/active_install_data.h',
       'browser/extensions/active_script_controller.cc',
@@ skipping 1046 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }