diff --git a/service_observer_interface.h b/service_observer_interface.h
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+++ b/service_observer_interface.h
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+//
+// Copyright (C) 2016 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+#ifndef UPDATE_ENGINE_SERVICE_OBSERVER_INTERFACE_H_
+#define UPDATE_ENGINE_SERVICE_OBSERVER_INTERFACE_H_
+
+#include <memory>
+#include <string>
+
+#include "update_engine/client_library/include/update_engine/update_status.h"
+
+namespace chromeos_update_engine {
+
+class ServiceObserverInterface {
+ public:
+  virtual ~ServiceObserverInterface() = default;
+
+  // Called whenever the value of these parameters changes. For |progress|
+  // value changes, this method will be called only if it changes significantly.
+  virtual void SendStatusUpdate(int64_t last_checked_time,
+                                double progress,
+                                update_engine::UpdateStatus status,
+                                const std::string& new_version,
+                                int64_t new_size) = 0;
+
+  // Called whenever the channel we are tracking changes.
+  virtual void SendChannelChangeUpdate(const std::string& tracking_channel) = 0;
+
+ protected:
+  ServiceObserverInterface() = default;
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_SERVICE_OBSERVER_INTERFACE_H_