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

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'variables': {
     # All .cc, .h, .m, and .mm files under browser except for:
     # * tests and mocks.
     # * code below browser/chromeos
     # * code below browser/extensions
@@ skipping 1077 matching lines @@
       'browser/importer/importer_uma.cc',
       'browser/importer/importer_uma.h',
       'browser/importer/in_process_importer_bridge.cc',
       'browser/importer/in_process_importer_bridge.h',
       'browser/importer/profile_writer.cc',
       'browser/importer/profile_writer.h',
       'browser/invalidation/ticl_profile_settings_provider.cc',
       'browser/invalidation/ticl_profile_settings_provider.h',
       'browser/lifetime/browser_close_manager.cc',
       'browser/lifetime/browser_close_manager.h',
+      'browser/lifetime/browser_keep_alive.cc',
+      'browser/lifetime/browser_keep_alive.h',
       'browser/media_galleries/fileapi/av_scanning_file_validator.cc',
       'browser/media_galleries/fileapi/av_scanning_file_validator.h',
       'browser/media_galleries/fileapi/device_media_async_file_util.cc',
       'browser/media_galleries/fileapi/device_media_async_file_util.h',
       'browser/media_galleries/fileapi/iapps_finder.h',
       'browser/media_galleries/fileapi/iapps_finder_impl.cc',
       'browser/media_galleries/fileapi/iapps_finder_impl.h',
       'browser/media_galleries/fileapi/iapps_finder_impl_mac.mm',
       'browser/media_galleries/fileapi/iapps_finder_impl_win.cc',
       'browser/media_galleries/fileapi/media_file_system_backend.cc',
@@ skipping 3010 matching lines @@
             '../components/components.gyp:omnibox_browser',
             '../components/components.gyp:rlz',
             '../components/components.gyp:search_engines',
             '../rlz/rlz.gyp:rlz_lib',
           ],
         },
       ],
     }],
   ],
 }