Exempt the Service Thread from BLOCK_SHUTDOWN DCHECKs

base/task_scheduler/task_scheduler_impl.cc

 // Copyright 2016 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.
 
 #include "base/task_scheduler/task_scheduler_impl.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 86 matching lines @@
       MessageLoop::TYPE_DEFAULT;
 #endif
   service_thread_options.timer_slack = TIMER_SLACK_MAXIMUM;
   CHECK(service_thread_.StartWithOptions(service_thread_options));
 
 #if defined(OS_POSIX) && !defined(OS_NACL_SFI)
   // Needs to happen after starting the service thread to get its
   // message_loop().
   task_tracker_.set_watch_file_descriptor_message_loop(
       static_cast<MessageLoopForIO*>(service_thread_.message_loop()));
-#endif
+
+#if DCHECK_IS_ON()
+  task_tracker_.set_service_thread_handle(service_thread_.GetThreadHandle());
+#endif  // DCHECK_IS_ON()
+#endif  // defined(OS_POSIX) && !defined(OS_NACL_SFI)
 
   // Needs to happen after starting the service thread to get its task_runner().
   delayed_task_manager_.Start(service_thread_.task_runner());
 
   single_thread_task_runner_manager_.Start();
 
   worker_pools_[BACKGROUND]->Start(init_params.background_worker_pool_params);
   worker_pools_[BACKGROUND_BLOCKING]->Start(
       init_params.background_blocking_worker_pool_params);
   worker_pools_[FOREGROUND]->Start(init_params.foreground_worker_pool_params);
@@ skipping 98 matching lines @@
   // in |sequence|.
   const TaskTraits traits =
       sequence->PeekTaskTraits().WithPriority(sort_key.priority());
 
   GetWorkerPoolForTraits(traits)->ReEnqueueSequence(std::move(sequence),
                                                     sort_key);
 }
 
 }  // namespace internal
 }  // namespace base