[Sync] Refactor ModelSafeWorker::DoWorkAndWaitUntilDone() to avoid code duplication.

components/password_manager/sync/browser/password_model_worker.h

Index: components/password_manager/sync/browser/password_model_worker.h
diff --git a/components/password_manager/sync/browser/password_model_worker.h b/components/password_manager/sync/browser/password_model_worker.h
index eb45efc7e311c4641b2f2cb428cae2ada398d0f4..c628e7f60f226e09ad2d4ceb5195f5e01dd15d3f 100644
--- a/components/password_manager/sync/browser/password_model_worker.h
+++ b/components/password_manager/sync/browser/password_model_worker.h
@@ -28,13 +28,11 @@ class PasswordModelWorker : public syncer::ModelSafeWorker {
   bool IsOnModelThread() override;
   void RequestStop() override;
 
- protected:
-  syncer::SyncerError DoWorkAndWaitUntilDoneImpl(
-      const syncer::WorkCallback& work) override;
-
  private:
   ~PasswordModelWorker() override;
 
+  void ScheduleWork(base::Closure work) override;
+
   // |password_store_| is used on password thread but released on UI thread.
   // Protected by |password_store_lock_|.
   base::Lock password_store_lock_;