Log the sync communication that happens between client and server.

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 71 matching lines @@
         'engine/syncer_command.h',
         'engine/syncer_proto_util.cc',
         'engine/syncer_proto_util.h',
         'engine/sync_scheduler.cc',
         'engine/sync_scheduler.h',
         'engine/syncer_types.cc',
         'engine/syncer_types.h',
         'engine/syncer_util.cc',
         'engine/syncer_util.h',
         'engine/syncproto.h',
+        'engine/traffic_logger.cc',
+        'engine/traffic_logger.h',
         'engine/update_applicator.cc',
         'engine/update_applicator.h',
         'engine/verify_updates_command.cc',
         'engine/verify_updates_command.h',
         'js/js_arg_list.cc',
         'js/js_arg_list.h',
         'js/js_backend.h',
         'js/js_controller.h',
         'js/js_event_details.cc',
         'js/js_event_details.h',
@@ skipping 240 matching lines @@
       'conditions': [
         ['OS=="linux" and linux_use_tcmalloc==1', {
           'dependencies': [
             '../base/allocator/allocator.gyp:allocator',
           ],
         }],
       ],
     },
   ],
 }