Extension syncing: Introduce a NeedsSync pref

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/enterprise_platform_keys/enterprise_platform_keys_api.cc',
       'browser/extensions/api/enterprise_platform_keys/enterprise_platform_keys_api.h',
       'browser/extensions/api/enterprise_platform_keys_private/enterprise_platform_keys_private_api.cc',
@@ skipping 761 matching lines @@
       'browser/extensions/menu_manager_factory.cc',
       'browser/extensions/menu_manager_factory.h',
       'browser/extensions/navigation_observer.cc',
       'browser/extensions/navigation_observer.h',
       'browser/extensions/ntp_overridden_bubble_controller.cc',
       'browser/extensions/ntp_overridden_bubble_controller.h',
       'browser/extensions/pack_extension_job.cc',
       'browser/extensions/pack_extension_job.h',
       'browser/extensions/path_util.cc',
       'browser/extensions/path_util.h',
-      'browser/extensions/pending_enables.cc',
-      'browser/extensions/pending_enables.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_based_management_policy_provider.cc',
       'browser/extensions/permissions_based_management_policy_provider.h',
       'browser/extensions/permissions_updater.cc',
       'browser/extensions/permissions_updater.h',
       'browser/extensions/plugin_manager.cc',
       'browser/extensions/plugin_manager.h',
@@ skipping 325 matching lines @@
           ],
         }, {  # use_brlapi==0
           'sources': [
             'browser/extensions/api/braille_display_private/braille_controller_stub.cc',
           ],
         }],
       ],
     },
   ],
 }