Add missing #include around sequenced_worker_pool.h

services/service_manager/standalone/context.h

 // Copyright 2013 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 SERVICES_SERVICE_MANAGER_STANDALONE_CONTEXT_H_
 #define SERVICES_SERVICE_MANAGER_STANDALONE_CONTEXT_H_
 
 #include <memory>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "services/service_manager/runner/host/service_process_launcher.h"
 #include "services/service_manager/standalone/tracer.h"
 #include "services/tracing/public/cpp/provider.h"
 
 namespace base {
+class SequencedWorkerPool;
 class Value;
 }
 
 namespace catalog {
 class Catalog;
 }
 
 namespace service_manager {
 
 class ServiceManager;
@@ skipping 23 matching lines @@
   std::unique_ptr<catalog::Catalog> catalog_;
   std::unique_ptr<ServiceManager> service_manager_;
   base::Time main_entry_time_;
 
   DISALLOW_COPY_AND_ASSIGN(Context);
 };
 
 }  // namespace service_manager
 
 #endif  // SERVICES_SERVICE_MANAGER_STANDALONE_CONTEXT_H_