[Sync] Add ProfileSyncService::GetModelTypeStoreFactory.

ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc

Index: ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc
diff --git a/ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc b/ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc
index 45b759c71e8af33ccf64210fb53bd5022060dd5a..ea0f45cd811944666e5abadc9c9156bc652c5e39 100644
--- a/ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc
+++ b/ios/chrome/browser/sync/ios_chrome_profile_sync_service_factory.cc
@@ -141,7 +141,11 @@ IOSChromeProfileSyncServiceFactory::BuildServiceInstanceFor(
   init_params.url_request_context = browser_state->GetRequestContext();
   init_params.debug_identifier = browser_state->GetDebugName();
   init_params.channel = ::GetChannel();
-  init_params.blocking_pool = web::WebThread::GetBlockingPool();
+  base::SequencedWorkerPool* blocking_pool = web::WebThread::GetBlockingPool();
+  init_params.blocking_task_runner =
+      blocking_pool->GetSequencedTaskRunnerWithShutdownBehavior(
+          blocking_pool->GetSequenceToken(),
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
 
   auto pss = base::MakeUnique<ProfileSyncService>(std::move(init_params));