Refactor extension handling code from AppShimHost into ExtensionAppShimHandler.

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': [
     {
       'target_name': 'apps',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 18 matching lines @@
         'app_restore_service.cc',
         'app_restore_service.h',
         'app_restore_service_factory.cc',
         'app_restore_service_factory.h',
         'app_shim/app_shim_handler_mac.cc',
         'app_shim/app_shim_handler_mac.h',
         'app_shim/app_shim_host_mac.cc',
         'app_shim/app_shim_host_mac.h',
         'app_shim/app_shim_host_manager_mac.h',
         'app_shim/app_shim_host_manager_mac.mm',
+        'app_shim/extension_app_shim_handler_mac.h',
+        'app_shim/extension_app_shim_handler_mac.cc',
         'field_trial_names.cc',
         'field_trial_names.h',
         'pref_names.cc',
         'pref_names.h',
         'prefs.cc',
         'prefs.h',
         'shortcut_manager.cc',
         'shortcut_manager.h',
         'shortcut_manager_factory.cc',
         'shortcut_manager_factory.h',
@@ skipping 46 matching lines @@
               'VCLinkerTool': {
                 'SubSystem': '2',  # Set /SUBSYSTEM:WINDOWS
               },
             },
           },
         ],
       },
     ],  # 'OS=="win"'
   ],  # 'conditions'
 }