Suppress sequence checks in SyncFileSystem on the shutdown phase

chrome/browser/sync_file_system/drive_backend/sync_task_manager.h

Index: chrome/browser/sync_file_system/drive_backend/sync_task_manager.h
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_task_manager.h b/chrome/browser/sync_file_system/drive_backend/sync_task_manager.h
index de03d5772cf98ce780cb3d589282a06eab7f85e0..656e6468239a44b66730adaaa603a6de9acd45ae 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_task_manager.h
+++ b/chrome/browser/sync_file_system/drive_backend/sync_task_manager.h
@@ -13,6 +13,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequence_checker.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/sync_file_system/drive_backend/task_dependency_manager.h"
 #include "chrome/browser/sync_file_system/sync_callbacks.h"
 #include "chrome/browser/sync_file_system/sync_status_code.h"
@@ -70,7 +71,8 @@ class SyncTaskManager {
   // If |maximum_background_tasks| is zero, all task runs as foreground task.
   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);
   virtual ~SyncTaskManager();
 
   // This needs to be called to start task scheduling.
@@ -120,6 +122,7 @@ class SyncTaskManager {
   bool IsRunningTask(int64 task_token_id) const;
 
   void DetachFromSequence();
+  bool ShouldTrackTaskToken() const;
 
  private:
   struct PendingTask {
@@ -195,6 +198,7 @@ class SyncTaskManager {
   TaskDependencyManager dependency_manager_;
 
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
+  scoped_refptr<base::SequencedWorkerPool> worker_pool_;
   base::SequenceChecker sequence_checker_;
 
   base::WeakPtrFactory<SyncTaskManager> weak_ptr_factory_;;