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 535 matching lines @@
         'browser/extensions/page_action_controller.cc',
         'browser/extensions/page_action_controller.h',
         'browser/extensions/pending_extension_info.cc',
         'browser/extensions/pending_extension_info.h',
         'browser/extensions/pending_extension_manager.cc',
         'browser/extensions/pending_extension_manager.h',
         'browser/extensions/permissions_updater.cc',
         'browser/extensions/permissions_updater.h',
         'browser/extensions/platform_app_launcher.cc',
         'browser/extensions/platform_app_launcher.h',
+        'browser/extensions/platform_app_service.cc',
+        'browser/extensions/platform_app_service.h',
         'browser/extensions/process_map.cc',
         'browser/extensions/process_map.h',
         'browser/extensions/requirements_checker.cc',
         'browser/extensions/requirements_checker.h',
         'browser/extensions/sandboxed_unpacker.cc',
         'browser/extensions/sandboxed_unpacker.h',
         'browser/extensions/script_badge_controller.cc',
         'browser/extensions/script_badge_controller.h',
         'browser/extensions/script_bubble_controller.cc',
         'browser/extensions/script_bubble_controller.h',
@@ skipping 308 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'
 }