[Sync] Move thread checking into the ModelSafeWorker interface.

chrome/browser/sync/profile_sync_test_util.cc

Index: chrome/browser/sync/profile_sync_test_util.cc
diff --git a/chrome/browser/sync/profile_sync_test_util.cc b/chrome/browser/sync/profile_sync_test_util.cc
index 38dcabb04772a12dbf836105f87b57d29252d4c2..c06b04f56078b2127358244c2362f614f03c8bfa 100644
--- a/chrome/browser/sync/profile_sync_test_util.cc
+++ b/chrome/browser/sync/profile_sync_test_util.cc
@@ -55,10 +55,6 @@ ProfileSyncService::InitParams CreateProfileSyncServiceParamsForTest(
   init_params.url_request_context = profile->GetRequestContext();
   init_params.debug_identifier = profile->GetDebugName();
   init_params.channel = chrome::GetChannel();
-  init_params.db_thread = content::BrowserThread::GetTaskRunnerForThread(
-      content::BrowserThread::DB);
-  init_params.file_thread = content::BrowserThread::GetTaskRunnerForThread(
-      content::BrowserThread::FILE);
   init_params.blocking_pool = content::BrowserThread::GetBlockingPool();
 
   return init_params;