Add shutdown notification and service refs to SyncServiceObserver.

chrome/browser/sync_file_system/sync_file_system_service.cc

Index: chrome/browser/sync_file_system/sync_file_system_service.cc
diff --git a/chrome/browser/sync_file_system/sync_file_system_service.cc b/chrome/browser/sync_file_system/sync_file_system_service.cc
index d9666744e376f6e72aa20c55ad2a0a83f8bdb7b0..2ea9673d28e4912d54e9098ddcd36057e8054ccf 100644
--- a/chrome/browser/sync_file_system/sync_file_system_service.cc
+++ b/chrome/browser/sync_file_system/sync_file_system_service.cc
@@ -728,11 +728,8 @@ void SyncFileSystemService::OnExtensionLoaded(
   local_service_->SetOriginEnabled(app_origin, true);
 }
 
-void SyncFileSystemService::OnStateChanged() {
-  syncer::SyncService* profile_sync_service =
-      ProfileSyncServiceFactory::GetSyncServiceForBrowserContext(profile_);
-  if (profile_sync_service)
-    UpdateSyncEnabledStatus(profile_sync_service);
+void SyncFileSystemService::OnStateChanged(syncer::SyncService* sync) {
+  UpdateSyncEnabledStatus(sync);
 }
 
 void SyncFileSystemService::OnFileStatusChanged(