AU: Beginnings of dbus support.

The AU will be a daemon that runs as root. Non-root will communicate
via dbus with the updater to do things such as: query status, request
forced or full updates, etc.

New files for dbus:

UpdateEngine.conf - security configuration
dbus_constants.h - common constants
dbus_service.* - The object exposed over dbus
org.chromium.UpdateEngine.service - the dbus service file
udpate_attempter.* - Refactored this out of main.cc
update_engine_client.cc - Simple command line utility to interact with
Update Engine over dbus. Whereas Update Engine runs as root, this tool
runs as non-root user.

Review URL: http://codereview.chromium.org/1733013
diff --git a/dbus_constants.h b/dbus_constants.h
new file mode 100644
index 0000000..bd5b551
--- /dev/null
+++ b/dbus_constants.h
@@ -0,0 +1,18 @@
+// Copyright (c) 2010 The Chromium OS 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 CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_CONSTANTS_H__
+#define CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_CONSTANTS_H__
+
+namespace chromeos_update_engine {
+
+static const char* const kUpdateEngineServiceName = "org.chromium.UpdateEngine";
+static const char* const kUpdateEngineServicePath =
+    "/org/chromium/UpdateEngine";
+static const char* const kUpdateEngineServiceInterface =
+    "org.chromium.UpdateEngineInterface";
+
+}  // namespace chromeos_update_engine
+
+#endif  // CHROMEOS_PLATFORM_UPDATE_ENGINE_DBUS_CONSTANTS_H__