Keep browser process alive while there are platform apps with background pages running.

chrome/chrome_browser_extensions.gypi

 # Copyright (c) 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': [
     {
       'target_name': 'browser_extensions',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 320 matching lines @@
         'browser/extensions/api/web_request/web_request_api_helpers.cc',
         'browser/extensions/api/web_request/web_request_api_helpers.h',
         'browser/extensions/api/web_request/web_request_permissions.cc',
         'browser/extensions/api/web_request/web_request_permissions.h',
         'browser/extensions/api/web_request/web_request_time_tracker.cc',
         'browser/extensions/api/web_request/web_request_time_tracker.h',
         'browser/extensions/api/web_socket_proxy_private/web_socket_proxy_private_api.cc',
         'browser/extensions/api/web_socket_proxy_private/web_socket_proxy_private_api.h',
         'browser/extensions/api/webstore_private/webstore_private_api.cc',
         'browser/extensions/api/webstore_private/webstore_private_api.h',
+        'browser/extensions/app_extension_host_delegate.cc',
+        'browser/extensions/app_extension_host_delegate.h',
         'browser/extensions/app_notification.cc',
         'browser/extensions/app_notification.h',
         'browser/extensions/app_notification_manager.cc',
         'browser/extensions/app_notification_manager.h',
         'browser/extensions/app_notification_storage.cc',
         'browser/extensions/app_notification_storage.h',
         'browser/extensions/app_notify_channel_setup.cc',
         'browser/extensions/app_notify_channel_setup.h',
         'browser/extensions/app_notify_channel_ui.h',
         'browser/extensions/app_notify_channel_ui_impl.cc',
@@ skipping 521 matching lines @@
             'browser/extensions/app_host/update.cc',
             'browser/extensions/app_host/update.h',
             '<(SHARED_INTERMEDIATE_DIR)/chrome_version/app_host_exe_version.rc',
           ],
         },
       ],
     }, ],  # 'OS=="win"'
   ],  # 'conditions'
 }