Remove #pragma once from sync

sync/notifier/sync_notifier_observer.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_
 #define SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_
-#pragma once
 
 #include "sync/internal_api/public/base/model_type_payload_map.h"
 #include "sync/notifier/notifications_disabled_reason.h"
 
 namespace syncer {
 
 enum IncomingNotificationSource {
   // The server is notifying us that one or more datatypes have stale data.
   REMOTE_NOTIFICATION,
   // A chrome datatype is requesting an optimistic refresh of its data.
@@ skipping 16 matching lines @@
       const syncer::ModelTypePayloadMap& type_payloads,
       IncomingNotificationSource source) = 0;
 
  protected:
   virtual ~SyncNotifierObserver() {}
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_NOTIFIER_SYNC_NOTIFIER_OBSERVER_H_