[Sync] Fixing easy lint violations.

components/sync/core/activation_context.h

 // Copyright 2015 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 COMPONENTS_SYNC_CORE_ACTIVATION_CONTEXT_H_
 #define COMPONENTS_SYNC_CORE_ACTIVATION_CONTEXT_H_
 
+#include <memory>
+
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/sequenced_task_runner.h"
 #include "components/sync/core/model_type_processor.h"
 #include "components/sync/core/non_blocking_sync_common.h"
 #include "components/sync/protocol/data_type_state.pb.h"
 
 namespace syncer {
 
 // The state passed from ModelTypeProcessor to Sync thread during DataType
 // activation.
 struct ActivationContext {
   ActivationContext();
   ~ActivationContext();
 
   // Initial DataTypeState at the moment of activation.
   sync_pb::DataTypeState data_type_state;
 
   // The ModelTypeProcessor for the worker. Note that this is owned because
   // it is generally a proxy object to the real processor.
   std::unique_ptr<ModelTypeProcessor> type_processor;
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_CORE_ACTIVATION_CONTEXT_H_