[Sync] Add support for automatic enabling of syncing tab favicons.

sync/sync.gyp

 # 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.
 
 {
   'variables': {
     'chromium_code': 1,
   },
   'targets': [
     # The core sync library.
@@ skipping 157 matching lines @@
         'util/immutable.h',
         'util/logging.cc',
         'util/logging.h',
         'util/nigori.cc',
         'util/nigori.h',
         'util/report_unrecoverable_error_function.h',
         'util/session_utils_android.cc',
         'util/session_utils_android.h',
         'util/syncer_error.cc',
         'util/syncer_error.h',
+        'util/sync_experiments.h',
         'util/time.cc',
         'util/time.h',
         'util/unrecoverable_error_handler.h',
         'util/unrecoverable_error_info.h',
         'util/unrecoverable_error_info.cc',
         'util/weak_handle.cc',
         'util/weak_handle.h',
       ],
     },
 
@@ skipping 437 matching lines @@
         '../net/net.gyp:net_test_support',
         'sync',
         'sync_notifier',
       ],
       'sources': [
         'tools/sync_listen_notifications.cc',
       ],
     },
   ],
 }