Remove #pragma once from sync

sync/js/js_backend.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_JS_JS_BACKEND_H_
 #define SYNC_JS_JS_BACKEND_H_
-#pragma once
 
 // See README.js for design comments.
 
 #include <string>
 
 namespace syncer {
 
 class JsArgList;
 class JsEventHandler;
 class JsReplyHandler;
@@ skipping 14 matching lines @@
       const std::string& name, const JsArgList& args,
       const WeakHandle<JsReplyHandler>& reply_handler) = 0;
 
  protected:
   virtual ~JsBackend() {}
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_JS_JS_BACKEND_H_