Suppress sequence checks in SyncFileSystem on the shutdown phase

chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc

Index: chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc b/chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc
index d6ecbae566798c7639729b29cb39acfbae907ac4..16e1f9bf53804206a0503fd3ff7820d2a9fb8695 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc
+++ b/chrome/browser/sync_file_system/drive_backend/sync_task_manager.cc
@@ -55,12 +55,14 @@ bool SyncTaskManager::PendingTaskComparator::operator()(
 SyncTaskManager::SyncTaskManager(
     base::WeakPtr<Client> client,
     size_t maximum_background_task,
-    const scoped_refptr<base::SequencedTaskRunner>& task_runner)
+    const scoped_refptr<base::SequencedTaskRunner>& task_runner,
+    const scoped_refptr<base::SequencedWorkerPool>& worker_pool)
     : client_(client),
       maximum_background_task_(maximum_background_task),
       pending_task_seq_(0),
       task_token_seq_(SyncTaskToken::kMinimumBackgroundTaskTokenID),
       task_runner_(task_runner),
+      worker_pool_(worker_pool),
       weak_ptr_factory_(this) {
 }
 
@@ -204,6 +206,10 @@ void SyncTaskManager::DetachFromSequence() {
   sequence_checker_.DetachFromSequence();
 }
 
+bool SyncTaskManager::ShouldTrackTaskToken() const {
+  return !worker_pool_ || !worker_pool_->IsShutdownInProgress();
+}
+
 void SyncTaskManager::NotifyTaskDoneBody(scoped_ptr<SyncTaskToken> token,
                                          SyncStatusCode status) {
   DCHECK(sequence_checker_.CalledOnValidSequencedThread());