Move CancelableTaskTracker to //base/task/CancelableTaskTracker.

base/base.gypi

 # 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.
 
 {
   'target_defaults': {
     'variables': {
       'base_target': 0,
       'base_i18n_target': 0,
     },
@@ skipping 554 matching lines @@
           'sys_info_android.cc',
           'sys_info_chromeos.cc',
           'sys_info_freebsd.cc',
           'sys_info_internal.h',
           'sys_info_ios.mm',
           'sys_info_linux.cc',
           'sys_info_mac.cc',
           'sys_info_openbsd.cc',
           'sys_info_posix.cc',
           'sys_info_win.cc',
+          'task/cancelable_task_tracker.cc',
+          'task/cancelable_task_tracker.h',
           'task_runner.cc',
           'task_runner.h',
           'task_runner_util.h',
           'template_util.h',
           'thread_task_runner_handle.cc',
           'thread_task_runner_handle.h',
           'threading/non_thread_safe.h',
           'threading/non_thread_safe_impl.cc',
           'threading/non_thread_safe_impl.h',
           'threading/platform_thread.h',
@@ skipping 389 matching lines @@
           'i18n/time_formatting.h',
           'i18n/timezone.cc',
           'i18n/timezone.h',
           'i18n/utf8_validator_tables.cc',
           'i18n/utf8_validator_tables.h',
         ],
       }]
     ],
   },
 }