update_engine: support DLC update
All DLC update related code is hide behind USE_dlc flag so platform
update never touches this new code path unless enabled later.
In CheckForUpdate, update_engine calls dlcservice to get a list of DLC
module and set 'dlc_ids_' accordingly.
BUG=chromium:900653
TEST=unittest
Change-Id: I654e37effa7c1b70b25147a027f2b16abe6bf9e1
Reviewed-on: https://chromium-review.googlesource.com/1321009
Commit-Ready: Xiaochu Liu <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
diff --git a/common/dlcservice.h b/common/dlcservice.h
new file mode 100644
index 0000000..9dae560
--- /dev/null
+++ b/common/dlcservice.h
@@ -0,0 +1,32 @@
+//
+// Copyright (C) 2018 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_COMMON_DLCSERVICE_H_
+#define UPDATE_ENGINE_COMMON_DLCSERVICE_H_
+
+#include <memory>
+
+#include "update_engine/common/dlcservice_interface.h"
+
+namespace chromeos_update_engine {
+
+// This factory function creates a new DlcServiceInterface instance for the
+// current platform.
+std::unique_ptr<DlcServiceInterface> CreateDlcService();
+
+} // namespace chromeos_update_engine
+
+#endif // UPDATE_ENGINE_COMMON_DLCSERVICE_H_