Suppress sequence checks in SyncFileSystem on the shutdown phase

chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc

Index: chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc b/chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc
index 867075eba3d74f39e2701166caac69db2a542f6d..e487003b215a2bf017c7ade45dfc6ba1f197b133 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc
+++ b/chrome/browser/sync_file_system/drive_backend/sync_engine_context.cc
@@ -23,14 +23,16 @@ SyncEngineContext::SyncEngineContext(
     scoped_ptr<drive::DriveUploaderInterface> drive_uploader,
     TaskLogger* task_logger,
     const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
-    const scoped_refptr<base::SequencedTaskRunner>& worker_task_runner)
+    const scoped_refptr<base::SequencedTaskRunner>& worker_task_runner,
+    const scoped_refptr<base::SequencedWorkerPool>& worker_pool)
     : drive_service_(drive_service.Pass()),
       drive_uploader_(drive_uploader.Pass()),
       task_logger_(task_logger ? task_logger->AsWeakPtr()
                                : base::WeakPtr<TaskLogger>()),
       remote_change_processor_(nullptr),
       ui_task_runner_(ui_task_runner),
-      worker_task_runner_(worker_task_runner) {
+      worker_task_runner_(worker_task_runner),
+      worker_pool_(worker_pool) {
   sequence_checker_.DetachFromSequence();
 }
 
@@ -78,6 +80,11 @@ base::SequencedTaskRunner* SyncEngineContext::GetWorkerTaskRunner() {
   return worker_task_runner_.get();
 }
 
+base::SequencedWorkerPool* SyncEngineContext::GetWorkerPool() {
+  DCHECK(sequence_checker_.CalledOnValidSequencedThread());
+  return worker_pool_.get();
+}
+
 void SyncEngineContext::SetMetadataDatabase(
     scoped_ptr<MetadataDatabase> metadata_database) {
   DCHECK(sequence_checker_.CalledOnValidSequencedThread());