[SyncFS] Introduce CallbackTracker to handle callback abortion

chrome/chrome_browser.gypi

 # Copyright 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.
 
 {
   'targets': [
     {
       'target_name': 'browser',
       'type': 'static_library',
       'variables': { 'enable_wexit_time_destructors': 1, },
@@ skipping 2303 matching lines @@
         'browser/sync/sync_policy_handler.cc',
         'browser/sync/sync_policy_handler.h',
         'browser/sync/sync_startup_tracker.cc',
         'browser/sync/sync_startup_tracker.h',
         'browser/sync/sync_ui_util.cc',
         'browser/sync/sync_ui_util.h',
         'browser/sync_file_system/conflict_resolution_policy.h',
         'browser/sync_file_system/conflict_resolution_resolver.cc',
         'browser/sync_file_system/conflict_resolution_resolver.h',
         'browser/sync_file_system/drive_backend/callback_helper.h',
+        'browser/sync_file_system/drive_backend/callback_tracker.cc',
+        'browser/sync_file_system/drive_backend/callback_tracker.h',
+        'browser/sync_file_system/drive_backend/callback_tracker_internal.h',
         'browser/sync_file_system/drive_backend/conflict_resolver.cc',
         'browser/sync_file_system/drive_backend/conflict_resolver.h',
         'browser/sync_file_system/drive_backend/drive_backend_constants.cc',
         'browser/sync_file_system/drive_backend/drive_backend_constants.h',
         'browser/sync_file_system/drive_backend/drive_backend_util.cc',
         'browser/sync_file_system/drive_backend/drive_backend_util.h',
         'browser/sync_file_system/drive_backend/drive_service_on_worker.cc',
         'browser/sync_file_system/drive_backend/drive_service_on_worker.h',
         'browser/sync_file_system/drive_backend/drive_service_wrapper.cc',
         'browser/sync_file_system/drive_backend/drive_service_wrapper.h',
@@ skipping 1419 matching lines @@
             'package_name': 'org/chromium/chrome/browser',
             'template_deps': ['browser/android/tab_load_status.h'],
           },
           'includes': [ '../build/android/java_cpp_template.gypi' ],
         },
       ],
      },
     ],
   ],
 }