Remove #pragma once from sync

sync/internal_api/js_mutation_event_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_INTERNAL_API_JS_MUTATION_EVENT_OBSERVER_H_
 #define SYNC_INTERNAL_API_JS_MUTATION_EVENT_OBSERVER_H_
-#pragma once
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "sync/internal_api/public/sync_manager.h"
 #include "sync/internal_api/public/util/weak_handle.h"
 #include "sync/syncable/transaction_observer.h"
@@ skipping 43 matching lines @@
   void HandleJsEvent(
     const tracked_objects::Location& from_here,
     const std::string& name, const JsEventDetails& details);
 
   DISALLOW_COPY_AND_ASSIGN(JsMutationEventObserver);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_JS_MUTATION_EVENT_OBSERVER_H_