Add return values to SyncerCommand

chrome/chrome.gyp

 # Copyright (c) 2011 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,
 
     'variables': {
       'version_py_path': 'tools/build/version.py',
       'version_path': 'VERSION',
@@ skipping 244 matching lines @@
     },
     {
       # Provides a syncapi dynamic library target from checked-in binaries,
       # or from compiling a stub implementation.
       'target_name': 'syncapi_core',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
       'sources': [
         'browser/sync/engine/syncapi_internal.cc',
         'browser/sync/engine/syncapi_internal.h',
+        'browser/sync/internal_api/includes/syncer_error.cc',
+        'browser/sync/internal_api/includes/syncer_error.h',
         'browser/sync/internal_api/includes/unrecoverable_error_handler.h',
         'browser/sync/internal_api/base_node.cc',
         'browser/sync/internal_api/base_node.h',
         'browser/sync/internal_api/base_transaction.cc',
         'browser/sync/internal_api/base_transaction.h',
         'browser/sync/internal_api/change_record.cc',
         'browser/sync/internal_api/change_record.h',
         'browser/sync/internal_api/change_reorder_buffer.cc',
         'browser/sync/internal_api/change_reorder_buffer.h',
         'browser/sync/internal_api/configure_reason.h',
@@ skipping 1049 matching lines @@
           'sources': [
             'browser/safe_browsing/signature_util.h',
             'browser/safe_browsing/signature_util_win.cc',
             'tools/safe_browsing/sb_sigutil.cc',
           ],
         },
       ]},  # 'targets'
     ],  # OS=="win"
   ],  # 'conditions'
 }