Implement update_engine weave commands

The new WeaveServiceInterface abstracs the registration and interaction
with weave whenever present. The compilation and usage of weave is
based on the BRILLO_USE_WEAVE flag.

When enabled, update_engine registers the "_updater" component with
methods to force-check for an update and change channels.

Bug: 24386758
Bug: 24386768
Test: Deployed on edison, weave commands and state available online.

Change-Id: Ic49111772e123b8a2b1971da92fe65785f186ccd
diff --git a/weave_service.h b/weave_service.h
new file mode 100644
index 0000000..6790d54
--- /dev/null
+++ b/weave_service.h
@@ -0,0 +1,53 @@
+//
+// Copyright (C) 2015 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_WEAVE_SERVICE_H_
+#define UPDATE_ENGINE_WEAVE_SERVICE_H_
+
+#include <memory>
+
+#include <dbus/bus.h>
+#include <libweaved/command.h>
+#include <libweaved/device.h>
+
+#include "update_engine/weave_service_interface.h"
+
+namespace chromeos_update_engine {
+
+class WeaveService : public WeaveServiceInterface {
+ public:
+  WeaveService() = default;
+  ~WeaveService() override = default;
+
+  bool Init(scoped_refptr<dbus::Bus> bus, DelegateInterface* delegate);
+
+  // WeaveServiceInterface override.
+  void UpdateWeaveState() override;
+
+ private:
+  // Weave command handlers. These are called from the message loop whenever a
+  // command is received and dispatch the synchronous call to the |delegate_|.
+  void OnCheckForUpdates(const std::weak_ptr<weaved::Command>& cmd);
+  void OnTrackChannel(const std::weak_ptr<weaved::Command>& cmd);
+
+  WeaveServiceInterface::DelegateInterface* delegate_{nullptr};
+
+  std::unique_ptr<weaved::Device> device_;
+};
+
+}  // namespace chromeos_update_engine
+
+#endif  // UPDATE_ENGINE_WEAVE_SERVICE_H_